R C S P Study Guide 199 01 V2.0.1

Riverbed Certified Solutions Professional (RCSP)
Study Guide
Exam 199-01 for RiOS v5.0

June, 2009
Version 2.0

RCSP Study Guide

COPYRIGHT © 2007-2009 Riverbed Technology, Inc.
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© 2007-2009 Riverbed Technology, Inc. All rights reserved. 1

RCSP Study Guide

Table of Contents
Preface ..................................................................................................................................................................................................................... 4
Certification Overview ............................................................................................................................................................................................ 4
Benefits of Certification......................................................................................................................................................................................... 4
Exam Information.................................................................................................................................................................................................. 4
Certification Checklist ........................................................................................................................................................................................... 5
Recommended Resources for Study.................................................................................................................................................................... 5
RIVERBED CERTIFIED SOLUTIONS PROFESSIONAL STUDY GUIDE .............................................................................................................. 7
I. General Knowledge ............................................................................................................................................................................................. 7
Optimizations Performed by RiOS........................................................................................................................................................................ 7
TCP/IP ................................................................................................................................................................................................................ 12
Common Ports.................................................................................................................................................................................................... 12
RiOS Auto-discovery Process ............................................................................................................................................................................ 13
Enhanced Auto-Discovery Process .................................................................................................................................................................... 14
Connection Pooling............................................................................................................................................................................................. 15
In-path Rules ...................................................................................................................................................................................................... 15
Peering Rules ..................................................................................................................................................................................................... 16
Steelhead Appliance Models and Capabilities ................................................................................................................................................... 17
II. Deployment ....................................................................................................................................................................................................... 19
In-path................................................................................................................................................................................................................. 20
Out-of-Band (OOB) Splice .................................................................................................................................................................................. 21
Virtual In-path ..................................................................................................................................................................................................... 23
Policy-Based Routing (PBR)............................................................................................................................................................................... 23
WCCP Deployments........................................................................................................................................................................................... 24
Advanced WCCP Configuration ......................................................................................................................................................................... 27
Server-Side Out-of-Path Deployments ............................................................................................................................................................... 28
Asymmetric Route Detection .............................................................................................................................................................................. 30
Connection Forwarding....................................................................................................................................................................................... 31
Simplified Routing (SR) ...................................................................................................................................................................................... 32
Data Store Synchronization ................................................................................................................................................................................ 33
CIFS Prepopulation ............................................................................................................................................................................................ 33
Authentication and Authorization........................................................................................................................................................................ 33
SSL ..................................................................................................................................................................................................................... 34
Central Management Console (CMC) ................................................................................................................................................................ 35
Steelhead Mobile Solution (Steelhead Mobile Controller & Steelhead Mobile Client) ....................................................................................... 36
Interceptor Appliance.......................................................................................................................................................................................... 37
III. Features ............................................................................................................................................................................................................ 40
Feature Licensing ............................................................................................................................................................................................... 40
HighSpeed TCP (HSTCP) .................................................................................................................................................................................. 40
MX-TCP .............................................................................................................................................................................................................. 42
Quality of Service................................................................................................................................................................................................ 42
PFS (Proxy File Service) Deployments .............................................................................................................................................................. 45
NetFlow............................................................................................................................................................................................................... 51
IPSec .................................................................................................................................................................................................................. 53
Operation on VLAN Tagged Links...................................................................................................................................................................... 53
IV. Troubleshooting .............................................................................................................................................................................................. 54
Common Deployment Issues.............................................................................................................................................................................. 54
Reporting and Monitoring ................................................................................................................................................................................... 56
Troubleshooting Best Practices.......................................................................................................................................................................... 59

2 © 2007-2009 Riverbed Technology, Inc. All rights reserved.

RCSP Study Guide

V. Exam Questions ............................................................................................................................................................................................... 61
Types of Questions............................................................................................................................................................................................. 61
Sample Questions .............................................................................................................................................................................................. 61
VI. Appendix .......................................................................................................................................................................................................... 65
Acronyms and Abbreviations .............................................................................................................................................................................. 65


RCSP Study Guide

Preface
This Riverbed Certification Study Guide is intended for anyone who wants to become certified in
the Riverbed Steelhead products and Riverbed Optimization System (RiOS). The Riverbed
Certified Solutions Professional (RCSP) program is designed to validate the skills required of
technical professionals who work in the implementation of Riverbed products.
This study guide provides a combination of theory and practical experience needed for a general
understanding of the subject matter. It also provides sample questions that will help in the
evaluation of personal progress and provide familiarity with the types of questions that will be
encountered in the exam.
This publication does not replace practical experience, nor is it designed to be a stand-alone
guide for any subject. Instead, it is an effective tool that, when combined with education
activities and experience, can be a very useful preparation guide for the exam.
Certification Overview
The Riverbed Certified Solutions Professional certificate is granted to individuals who
demonstrate advanced knowledge and experience with the RiOS product suite. The typical RCSP
will have taken a Riverbed approved training class such as the Steelhead Appliance Deployment
& Management course in addition to having hands-on experience in performing deployment,
troubleshooting, and maintenance of RiOS products in small, medium, and large organizations.
While there are no set requirements prior to taking the exam, candidates who have taken a
Riverbed authorized training class and have at least six months of hands-on experience with
RiOS products have a significantly higher chance of receiving the certification. We would like to
emphasize that solely taking the class will not adequately prepare you for the exam.
To obtain the RCSP certification, you are required to pass a computerized exam available at any
Pearson VUE testing center worldwide.
Benefits of Certification
1. Establishes your credibility as a knowledgeable and capable individual in regard to
Riverbed's products and services.
2. Helps improve your career advancement potential.
3. Qualifies you for discounts and/or benefits for Riverbed sponsored events and training.
4. Entitles you to use the RCSP certification logo on your business card.
Exam Information
Exam Specifications
• Exam Number: 199-01
• Exam Name: Riverbed Certified Solutions Professional
• Version of RiOS: Up to RiOS version 5.0 for the Steelhead appliances and the Central
Management Console, and Interceptor 2.0 and Steelhead Mobile 2.0
• Number of Questions: 65
• Total Time: 75 minutes for exam, 15 minutes for Survey and Tutorial (90 minutes total)
• Exam Provider: Pearson VUE
• Exam Language: English only. Riverbed allows a 30-minute time extension for English
exams taken in non-English speaking countries for students that request it. English speaking
countries are Australia, Bermuda, Canada, Great Britain, Ireland, New Zealand, Scotland,


RCSP Study Guide

South Africa, and the United States. A form will need to be completed by the candidate and
submitted to Pearson VUE.
• Special Accommodations: Yes (must submit written request to Pearson VUE for ESL or
ADA accommodations; includes time extensions and/or a reader)
• Offered Locations: Worldwide (over 5000 test centers in 165 countries)
• Pre-requisites: None (although taking a Riverbed training class is highly recommended)
• Available to: Everyone (partners, customers, employees, etc)
• Passing Score: 700 out of 1000 (70%)
• Certification Expires: Every 2 years (must recertify every 2 years, no grace period)
• Wait Between Failed Attempts: 72 hours. No retakes allowed on passed exams.
• Cost: $150.00 (USD)
• Number of Attempts Allowed: Unlimited (though statistics are kept)
Certification Checklist
As the RCSP exam is geared towards individuals who have both the theoretical knowledge and
hands on experience with the RiOS product suite, ensuring proficiency in both areas is crucial
towards passing the exam. For individuals starting out with the process, we recommend the
following steps to guide you along the way:
1. Building Theoretical Knowledge
The easiest way to become knowledgeable in deploying, maintaining, and troubleshooting
the RiOS product suite is to take a Riverbed authorized training class. To ensure the greatest
possibility of passing the exam, it is recommended that you review the RCSP Study Guide
and ensure your familiarity with all topics listed, prior to any examination attempts.
2. Gaining Hands-on Experience
While the theoretical knowledge will get you partway there, it is the hands-on knowledge
that can get you over the top and enable you to pass the exam. Since all deployments are
different, providing an exact amount of experience required is difficult. Generally, we
recommend that resellers and partners perform at least five deployments in a variety of
technologies prior to attempting the exam. For customers, and alternatively for resellers and
partners, starting from the design and deployment phase and having at least six months of
experience in a production environment would be beneficial.
3. Taking the Exam
The final step in becoming an RCSP is to take the exam at a Pearson VUE authorized testing
center. To register for any Riverbed Certification exam, please visit
http://www.pearsonvue.com/riverbed.
Recommended Resources for Study
Riverbed Training Courses
Information on Riverbed Training can be found at: http://www.riverbed.com/services/training/.
• Steelhead Appliance Deployment & Management
• Steelhead Appliance Operations & L1/L2 Troubleshooting
• Steelhead Mobile Installation & Configuration
• Central Management Console Configuration & Operations
• Interceptor Appliance Installation & Configuration


RCSP Study Guide

• Steelhead Appliance Advanced Deployment & Troubleshooting
Publications
Recommended Reading (In No Particular Order)
• This study guide
• Riverbed documentation
o Steelhead Management Console User's Guide
o Steelhead Command-Line Interface Reference Guide
o Steelhead Appliance Deployment Guide
o Steelhead Appliance Installation Guide
o Bypass Card Installation Guide
o Steelhead Mobile Controller User’s Guide
o Steelhead Mobile Controller Installation Guide
o Central Management Console User's Guide
o Central Management Console Installation Guide
o Interceptor Appliance User's Guide
o Interceptor Appliance Installation Guide
Other Reading (URLs Subject to Change)
• http://www.ietf.org/rfc.html
o RFC 793 (Original TCP RFC)
o RFC 1323 TCP extensions for high performance
o RFC 3649 (HighSpeed TCP for Large Congestion Windows)
o RFC 3742 (Limited Slow-Start for TCP with Large Congestion Windows)
o RFC 2474 (Differentiated Services Code Point)
• http://www.caida.org/tools/utilities/flowscan/arch.xml (NetFlow Protocol and Record
Headers)
• http://ubiqx.org/cifs/Intro.html (CIFS)
• Microsoft Windows 2000 Server Administrator’s Companion by Charlie Russell and Sharon
Crawford (Microsoft Press, 2000)
• Common Internet File System (CIFS) Technical Reference by the Storage Networking
Industry Association (Storage Networking Industry Association, 2002)
• TCP/IP Illustrated, Volume I, The Protocols by W. R. Stevens (Addison-Wesley, 1994)
• Internet Routing Architectures (2nd Edition) by Bassam Halabi (Cisco Press, 2000)


RCSP Study Guide

RIVERBED CERTIFIED SOLUTIONS PROFESSIONAL STUDY GUIDE
The Riverbed Certified Solutions Professional exam, and therefore this study guide, covers the
Riverbed products and technologies through RiOS version 5.0 only (Interceptor 2.0 and
Steelhead Mobile 2.0 as well).
I. General Knowledge
Optimizations Performed by RiOS
Optimization is the process of increasing data throughput and network performance over the
WAN using Steelhead appliances. An optimized connection exhibits bandwidth reduction as it
traverses the WAN. The optimization techniques RiOS utilizes are:
• Data Streamlining
• Transport Streamlining
• Application Streamlining
• Management Streamlining
You should be familiar with the differences in these streamlining techniques for the RCSP test.
This information can be found in the Steelhead Appliance Deployment Guide.
Transaction Acceleration (TA)
TA is composed of the following optimization mechanisms:
• A connection bandwidth-reducing mechanism called Scalable Data Referencing (SDR)
• A Virtual TCP Window Expansion (VWE) mechanism that repacks TCP payloads with
references that represent arbitrary amounts of data, thus increasing the client-data per WAN
TCP window
• A latency reduction and avoidance mechanism called Transaction Prediction
SDR and TP can work independently or in conjunction with one another depending on the
characteristics and workload of the data sent across the network. The results of the optimization
vary, but often result in throughput improvements in the range of 10 to 100 times over
unaccelerated links.
Scalable Data Referencing (SDR)
Bandwidth optimization is delivered through SDR. SDR uses a proprietary algorithm to break up
TCP data streams into data chunks that are stored in the hard disk (data store) of the Steelhead
appliances. Each data chunk is assigned a unique integer label (reference) before it is sent to the
peer Steelhead appliance across the WAN. If the same byte sequence is seen again in the TCP
data stream, then the reference is sent across the WAN instead of the raw data chunk. The peer
Steelhead appliance uses this reference to reconstruct the original data in the TCP data stream.
Data and references are maintained in persistent storage in the data store within each Steelhead
appliance. Because SDR checks data chunks byte-by-byte there are no consistency issues even in
the presence of replicated data.
How Does SDR Work?
When data is sent for the first time across a network (no commonality with any file ever sent
before), all data and references are new and are sent to the Steelhead appliance on the other side
of the network. This new data and the accompanying references are compressed using
conventional algorithms so as to improve performance, even on the first transfer.


RCSP Study Guide

Over time, more data crosses the network (revisions of a document for example). Thereafter,
when these new requests are sent across the network, the data is compared with references that
already exist in the local data store. Any data that the Steelhead appliance determines already
exists on the far side of the network are not sent—only the references are sent across the
network.
As files are copied, edited, renamed, and otherwise changed or moved (as well as web pages
being viewed or email sent), the Steelhead appliance continually builds the data store to include
more and more data and references. References can be shared by different files and by files in
different applications if the underlying bits are common to both. Since SDR can operate on all
TCP-based protocols, data commonality across protocols can be leveraged so long as the binary
representation of that data does not change between the protocols. For example, when a file
transferred via FTP is then transferred using WFS (Windows File System), the binary
representation of the file is basically the same and thus references can be sent for that file.
Lempel-Ziv (LZ) Compression
SDR and compression are two different features and can be controlled separately. However, LZ
compression is the primary form of data reduction for cold transfers.
The Lempel-Ziv compression methods are among the most popular algorithms for lossless
storage. Compression is turned on by default. In-path rules can be used to define which
optimization features will be used for which set of traffic flowing through the Steelhead
appliance.
TCP Optimizations & Virtual Window Expansion (VWE)
As Steelhead appliances are designed to optimize data transfers across wide area networks, they
make extensive use of standards-based enhancements to the TCP protocol that may not be
present in the TCP stack of many desktop and server operating systems. This includes improved
transport capability for networks with high bandwidth delay products via the use of HighSpeed
TCP, MX-TCP, or TCP Vegas for lower bandwidth links, partial acknowledgements, and other
more obscure but throughput enhancing and latency reducing features.
VWE allows Steelhead appliances to repack TCP payloads with references that represent
arbitrary amounts of data. This is possible because Steelhead appliances operate at the
Application Layer and terminate TCP, which gives them more flexibility in the way they
optimize WAN traffic.
Essentially, the TCP payload is increased from its normal window size to an arbitrarily large
amount dependent on the compression ratio for the connection. Because of this increased
payload, a given application that relies on TCP performance (for example, HTTP or FTP) takes
fewer trips across the WAN to accomplish the same task. For example, consider a client-to-
server connection that may have a 64KB TCP window. In the event that there is 256KB of data
to transfer, it would take several TCP windows to accomplish this in a network with high
latency. With SDR however, that 256KB of data can be potentially reduced to fit inside a single
TCP window, removing the need to wait for acknowledgements to be sent prior to sending the
next window, and thus speed the transfer.
Transaction Prediction
Application-level latency optimization is delivered through the Transaction Prediction module.
Transaction Prediction leverages an intimate understanding of protocol semantics to reduce the
chattiness that would normally occur over the WAN. By acting on foreknowledge of specific
protocol request-response mechanisms, Steelhead appliances streamline the delivery of data that


RCSP Study Guide

would normally be delivered in small increments through large numbers of interactions between
the client and server over the WAN. As transactions are executed between the client and server,
the Steelhead appliance intercepts each transaction, compares it to the database of past
transactions, and makes decisions about the probability of future events.
Based on this model, if a Steelhead appliance determines there is a high likelihood of a future
transaction occurring, it performs that transaction, rather than waiting for the response from the
server to propagate back to the client and then back to the server. Dramatic performance
improvements result from the time saved by not waiting for each serial transaction to arrive prior
to making the next request. Instead, the transactions are pipelined one right after the other.
Of course, transactions are executed by Steelhead appliances ahead of the client only when it is
safe to do so. To ensure data integrity, Steelhead appliances are designed with knowledge of the
underlying protocols to know when it is safe to do so. Fortunately, a wide range of common
applications have very predictable behaviors and, consequently, Transaction Prediction can
enhance WAN performance significantly. When combined with SDR, Transaction Prediction can
improve WAN performance up to 100 times.
Common Internet File System (CIFS) Optimization
CIFS is a proposed standard protocol that lets programs make requests for files and services on
remote computers over the Internet. CIFS uses the client/server programming model. A client
program makes a request of a server program (usually in another computer) for access to a file or
to pass a message to a program that runs in the server computer. The server takes the requested
action and returns a response. CIFS is a public or open variation of the Server Message Block
(SMB) protocol developed and used by Microsoft.
In the Steelhead appliance, CIFS optimization is enabled by default. Typically, you would only
disable CIFS optimization to troubleshoot the system.
Overlapping Opens
Due to the way certain applications handle the opening of files, file locks are not properly
granted to the application in such a way that would allow a Steelhead appliance to optimize
access to that file using Transaction Prediction. To prevent any compromise to data integrity, the
Steelhead appliance only optimizes data to which exclusive access is available (in other words,
when locks are granted). When an opportunistic lock (oplock) is not available, the Steelhead
appliance does not perform application-level latency optimizations but still performs SDR and
compression on the data as well as TCP optimizations. The CIFS overlapping opens feature
remedies this problem by having the server-side Steelhead handle file locking operations on
behalf of the requesting application. If you disable this feature, the Steelhead appliance will still
increase WAN performance, but not as effectively.
Enabling this feature on applications that perform multiple opens of the same file to complete an
operation will result in a performance improvement (for example, CAD applications).
NOTE: For the Steelhead appliance to handle the locking properly, all transactions on the file
must be optimized by that Steelhead appliance. Therefore, if a remote user opens a file which is
optimized using the overlapping opens feature, and a second user opens the same file they might
receive an error if the file fails to go through a Steelhead appliance or if it does not go through
the Steelhead appliance (for example, certain applications that are sent over the LAN). If this
occurs, you should disable overlapping opens optimizations for those applications.


RCSP Study Guide

Messaging Application Programming Interface (MAPI) Optimization
MAPI optimization is enabled by default. Only uncheck this box if you want to disable MAPI
optimization. Typically, you disable MAPI optimization to troubleshoot problems with the
system. For example, if you are experiencing problems with Microsoft Outlook clients
connecting to Exchange, you can disable MAPI latency acceleration (while continuing to
optimize with SDR for MAPI).
• Read ahead on attachments
• Read ahead on large emails
• Write behind on attachments
• Write behind on large emails
• Fails if user authentication set too high (downgrades to SDR/TCP acceleration only, no
Transaction Prediction)
MAPI Prepopulation
Without MAPI prepopulation, if a user closes Microsoft Outlook or switches off the workstation
the TCP sessions are broken. With MAPI prepopulation, the Steelhead appliance can start acting
as if it is the mail client. If the client closes the connection, the client-side Steelhead appliance
will keep an open connection to the server-side Steelhead appliance and the server-side
Steelhead appliance will keep the connection open to the server. This allows for data to be
pushed through the data store before the user logs on to the server again. The default timer is set
to 96 hours, after that, the connection will be reset.
• Optimized MAPI connections held open after client exit (acts like the client left the PC on);
think of it as virtual client
• Keep reading mail until timeout
• No one is ever reconnected to the prepopulation session (including the original user)
• No need for more Client Access Licenses (CALs); no agents to deploy
• Can configure frequency check and timeout or to disable it
• Enables transmission during off times even in consolidated environments
• The feature can be disabled independently from other MAPI optimizations
HTTP Optimization
A typical web page is not a single file that is downloaded all at once. Instead, web pages are
composed of dozens of separate objects—including .jpg and .gif images, JavaScript code,
cascading style sheets, and more—each of which must be requested and retrieved separately, one
after the other. Given the presence of latency, this behavior is highly detrimental to the
performance of web-based applications over the WAN.
The higher the latency, the longer it takes to fetch each individual object and, ultimately, to
display the entire page.
RiOS v5.0 and later optimizes web applications using:
• Parsing and Prefetching of Dynamic Content
• URL Learning


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• Removal of Unfetchable Objects
• HTTP Metadata Responses
• Persistent Connections
More information can be found in the Steelhead Appliance Management Console User’s Guide.
NFS Optimization
You can configure Steelhead appliances to use Transaction Prediction to perform application-
level latency optimization on NFS. Application-level latency optimization improves NFS
performance over high latency WANs.
NFS latency optimization optimizes TCP connections and is only supported for NFS v3.
You can configure NFS settings globally for all servers and volumes, or you can configure NFS
settings that are specific to particular servers or volumes. When you configure NFS settings for a
server, the settings are applied to all volumes on that server unless you override settings for
specific volumes.
• Read-ahead and read caching (checks freshness with modify date)
• Write-behind
• Metadata prefetching and caching
• Convert multiple requests into one larger request
• Special symbolic link handling
Microsoft SQL Optimization
Steelhead appliance MS SQL protocol support includes the ability to perform prefetching and
synthetic pre-acknowledgement of queries on database applications. By default, rules that
increase optimization for Microsoft Project Enterprise Edition ship with the unit. This
optimization is not enabled by default, and enabling MS SQL optimization without adding
specific rules will rarely have an effect on any other applications. MS SQL packets must be
carried in TDS (Tabular Data Stream) format for a Steelhead appliance to be able to perform
optimization.
You can also use MS SQL protocol optimization to optimize other database applications, but you
must define SQL rules to obtain maximum optimization. If you are interested in enabling the MS
SQL feature for other database applications, contact Riverbed Professional Services.
Oracle Forms Optimization
The Oracle Java Initiator (Jinitiator) or Oracle Forms is a browser plug-in program that accesses
Oracle E-Business application content and Oracle forms applications directly within a web
browser.
The Steelhead appliance decrypts, optimizes, and then re-encrypts Oracle Forms native and
HTTP mode traffic.
Use Oracle Forms optimization to improve Oracle Forms traffic performance. Oracle Forms does
not need a separate license and is enabled by default. However, you must also set an in-path rule
to enable this feature.


RCSP Study Guide

TCP/IP
General Operation
Steelhead appliances are typically placed on two ends of the WAN as close to the client and
server as possible (no additional WAN links between the end node and the Steelhead appliance).
By placing Steelhead appliances in the network, the TCP session between client and server can
be intercepted, therefore a level of control over the TCP session can be obtained. TCP sessions
have to be intercepted in order to be optimized; therefore the Steelhead appliances must see all
traffic from source to destination and back. For any given optimized session, there are three
distinct sessions. There is a TCP connection between the client and the client-side Steelhead
appliance, between the server and the server-side Steelhead appliance, and finally a connection
between the two Steelhead appliances.
Common Ports
Ports Used by RiOS
Port Type
7744 Data store sync port
7800 In-path port
7801 NAT port
7810 Out-of-path port
7820 Failover port for redundant appliances
7830 Exchange traffic port
7840 Exchange Director NSPI traffic port
7850 Connection Forwarding (neighbor) port
7860 Interceptor Appliance
7870 Steelhead Mobile

Interactive Ports Commonly Passed Through by Default on Steelhead Appliances (Partial
List)
Port Type
7 TCP ECHO
23 Telnet
37 UDP/Time
107 Remote Telnet Service
179 Border Gateway Protocol
513 Remote Login
514 Shell
1494, 2598 Citrix
3389 MS WBT, TS/Remote Desktop
5631 PC Anywhere


RCSP Study Guide

Port Type
5900 - 5903 VNC
600 X11

Secure Ports Commonly Passed Through by Default on Steelhead Appliances (Partial List)
Port Type
22/TCP ssh
49/TCP tacacs
443/TCP https
465/TCP smtps
563/TCP nntps
585/TCP imap4-ssl
614/TCP sshell
636/TCP ldaps
989/TCP ftps-data
990/TCP ftps
992/TCP telnets
993/TCP imaps
995/TCP pop3s
1701/TCP l2tp
1723/TCP pptp
3713/TCP tftp over tls

RiOS Auto-discovery Process
Auto-discovery is the process by which the Steelhead appliance automatically intercepts and
optimizes traffic on all IP addresses and ports. By default, auto-discovery is applied to all IP
addresses and the ports which are not secure, interactive, or Riverbed well-known ports.
Packet Flow
The following diagram shows the first connection packet flow for traffic that is classified as to be
optimized for the original auto-discovery protocol. The TCP SYN sent by the client is
intercepted by the Steelhead appliance. A TCP option is attached in the TCP header; this allows
the remote Steelhead appliance to recognize that there is a Steelhead appliance on the other side
of the network. When the server-side Steelhead appliance sees the option (also known as a TCP
probe) it responds to the option by sending a TCP SYN/ACK back. After auto-discovery has
taken place, the Steelhead appliances continue to set up the TCP inner session and the TCP outer
sessions.


RCSP Study Guide

Client SH1 SH2 Server

IP(C)→IP(S):SYN
IP(C)→IP(S):SYN+Probe
Announces service port
IP(S)→IP(C):SYN/ACK+Probe rsp (SH2) (default = TCP port 7800)
Probe result is
cached for 10 sec
IP(SH1)→IP(SH2):SYN

IP(SH2)→IP(SH1):SYN/ACK

IP(SH1)→IP(SH2):ACK

Setup Information

IP(C)→IP(S):SYN

IP(S)→IP(C):SYN/ACK
Connect Result
IP(C)→IP(S):ACK
Connect result is
IP(C)→IP(S):ACK cached until failure

Connection Pool:
20x

TCP Option
The TCP option used for auto-discovery is 0x4C which is 76 in decimal format. The client-side
Steelhead appliance attaches a 10 byte option to the TCP header; the server-side Steelhead
appliance attaches a 14 byte option in return. Note that this is only done in the initial discovery
process and not during connection setup between the Steelhead appliances and the outer TCP
sessions.
Enhanced Auto-Discovery Process
In RiOS v4.0.x or later, enhanced auto-discovery (EAD) is available. Enhanced auto-discovery
automatically discovers the last Steelhead appliance in the network path of the TCP connection.
In contrast, the original auto-discovery protocol automatically discovers the first Steelhead
appliance in the path. The difference is only seen in environments where there are three or more
Steelhead appliances in the network path for connections to be optimized.
Enhanced auto-discovery works with Steelhead appliances running the original auto-discovery
protocol. Enhanced auto-discovery ensures that a Steelhead appliance only optimizes TCP
connections that are being initiated or terminated at its local site, and that a Steelhead appliance
does not optimize traffic that is transiting through its site.


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Client SH1 SH2 Server
We are still using 0x4c but we now
use two of them (back-to-back)
IP(C)→IP(S):SYN SEQ1 Notification is being sent to SH1
IP(C)→IP(S):SYN SEQ1 +Probe
IP(C)→IP(S):SYN SEQ2 + Probe
Probe result is
cached for 10 sec Notification: not the last SH
IP(S)→IP(C):SYN/ACK+Probe rsp (S-SH)
Connect result is IP(C)→IP(S):ACK
acknum Connection Result
cached until failure
IP(SH1)→IP(SH2):SYN
Listening on
IP(SH2)→IP(SH1):SYN/ACK Service Port 7800
IP(SH1)→IP(SH2):ACK

Setup Information

IP(C)→IP(S):ACK

20x

Connection Pooling
General Operation
By default, all auto-discovered Steelhead appliance peers will have a default connection pool of
20. The connection pool is a user configurable value which can be configured for each Steelhead
appliance peer. The purpose of connection pooling is to avoid the TCP handshake for the inner
session between the Steelhead appliances across the high latency WAN. By pre-creating these
sessions between peer Steelhead appliances, when a new connection request is made by a client,
the client-side Steelhead appliance can simply use the connections in the pool. Once a
connection is pulled from the pool, a new connection is created to take its place so as to maintain
the specified number of connections.
In-path Rules
General Operation
In-path rules allow a client-side Steelhead appliance to determine what action to perform when
intercepting a new client connection (the first TCP SYN packet for a connection). The action
taken depends on the type of in-path rule selected and is outlined in detail below. It is important
to note that the rules are matched based on source/destination IP information, destination port,
and/or VLAN, and are processed from the first rule in the list to the last (top down). The rules
processing stops when the first rule matching the parameters specified is reached, at which point
the action selected by the rule is taken. Steelhead appliances have three passthrough rules by
default, and a fourth implicit rule to auto-discover remote Steelhead appliances. They attempt to
optimize traffic if the first three rules are not matched by traffic. The three default passthrough
rules include port groupings matching interactive traffic (i.e., Telnet, VNC, RDP), encrypted
traffic (i.e., server-side Steelhead), and Riverbed related used ports (i.e., 7800, 7810).
Different Types and Their Function
• Pass Through. Pass through rules identify traffic that is passed through the network
unoptimized. For example, you may define pass through rules to exclude subnets from


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optimization. Traffic is also passed through when the Steelhead appliance is in bypass mode.
(Passthrough might occur because of in-path rules, because the connection was established
before the Steelhead appliance was put in place, or before the Steelhead service was
enabled.)
• Fixed-Target. Fixed-target rules specify out-of-path Steelhead appliances near the target
server that you want to optimize. Determine which servers you want the Steelhead appliance
to optimize (and, optionally which ports), and add rules to specify the network of servers,
ports, port labels, and out-of-path Steelhead appliances to use. Fixed-target rules can also be
used for in-path deployments for Steelhead appliances not using EAD.
• Auto Discover. Auto-discovery is the process by which the Steelhead appliance
automatically intercepts and optimizes traffic on all IP addresses and ports. By default, auto-
discovery is applied to all IP addresses and the ports which are not secure, interactive, or
default Riverbed ports. Defining in-path rules modifies this default setting.
• Discard. Packets for the connection that match the rule are dropped silently. The Steelhead
appliance filters out traffic that matches the discard rules. This process is similar to how
routers and firewalls drop disallowed packets; the connection-initiating device has no
knowledge of the fact that its packets were dropped until the connection times out.
• Deny. When packets for connections match the deny rule, the Steelhead appliance actively
tries to reset the connection. With deny rules, the Steelhead appliance actively tries to reset
the TCP connection being attempted. Using an active reset process rather than a silent
discard allows the connection initiator to know that its connection is disallowed.
Peering Rules
Applicability and Conditions of Use
Peering Rules
Configuring peering rules defines what to do when a Steelhead appliance receives an auto-
discovery probe from another Steelhead appliance. As such, the scope of a peering rule is limited
to a server-side Steelhead appliance (the one receiving the probe). Note that peering rules on an
intermediary Steelhead appliance (or server-side) will have no effect in preventing optimization
with a client-side Steelhead appliance if it is using a fixed-target rule designating the
intermediary Steelhead appliance as its destination (since there is no auto-discovery probe in a
fixed-target rule). The following example shows where you might wish to use peering rules:
Site A Site B Site C
Client Steelhead1 Steelhead2 Steelhead3 Server 2

WAN 1 WAN 2

Server 1

Server1 is on the same LAN as Steelhead2 so connections from the client to Server1 should be
optimized between Steelhead1 and Steelhead2. Concurrently, Server2 is on the same LAN as
Steelhead3 and connections from the client to Server2 should be optimized between Steelhead1
and Steelhead3.


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• You do not need to define any rules on Steelhead1 or Steelhead3
• Add peering rules on Steelhead2 to process connections normally going to Server1 and to
pass through all other connections so that connections to Server2 are not optimized by
Steelhead2
• A rule to pass through inner connections between Steelhead1 and Steelhead3 is already in
place by default (by default connection to destination port 7800 is included by port label
“RBT-Proto”)
This configuration causes connections going to Server1 to be intercepted by Steelhead2, and
connections going to anywhere else to be intercepted by another Steelhead appliance (for
example, Steelhead3 for Server2).
Overcoming Peering Issues Using Fixed-Target Rules
If you do not enable automatic peering or define peering rules as described in the previous
sections, you must define:
• A fixed-target rule on Steelhead1 to go to Steelhead3 for connections to Server2
• A fixed-target rule on Steelhead3 to go to Steelhead1 for connections to servers in the same
site as Steelhead1
• If you have multiple branches that go through Steelhead2, you must add a fixed-target rule
for each of them on Steelhead1 and Steelhead3
Steelhead Appliance Models and Capabilities
Model Specifications (subject to change)

Steelhead Appliance Ports
A Steelhead appliance has Console, AUX, Primary, and WAN and LAN ports.
• The Primary and AUX ports cannot share the same network subnet
• The Primary and In-path interfaces can share the same network subnet
• You must use the Primary port on the server-side for out-of-path deployment


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• You can not use the Auxiliary port except for management
• If the Steelhead appliance is deployed between two switches, both the LAN and WAN ports
must be connected with straight-through cables
Interface Naming Conventions
The interface names for the bypass cards are a combination of the slot number and the port pairs
(<slot>_<pair>, <slot>_<pair>). For example, if a four-port bypass card is located in slot 0 of
your appliance, the interface names are: lan0_0, wan0_0, lan0_1, and wan0_1 respectively.
Alternatively, if the bypass card is located in slot 1 of your appliance, the interface names are:
lan1_0, wan1_0, lan1_1, and wan1_1 respectively.
The maximum number of copper LAN-WAN pairs (total paths) is ten; two built-in with a four-
port card, six with two six-port cards, and then two for a four-port card – for a maximum of ten
pairs.


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II. Deployment
Deployment Methods
Physical In-path
In a physical in-path deployment, the Steelhead appliance is physically in the direct path network
traffic will take between clients and servers. The clients and servers continue to see client and
server IP addresses and the Steelhead appliance bridges unoptimized traffic from its LAN facing
side to its WAN facing side (and vice versa). Physical in-path configurations are suitable for any
location where the total bandwidth is within the limits of the installed Steelhead appliance or
serial cluster of Steelhead appliances. It is generally one of the simplest deployment options and
among the easiest to maintain.
Logical In-path
In a logical in-path deployment, the Steelhead appliance is logically in the path between clients
and servers. In a logical in-path deployment, clients and servers continue to see client and server
IP addresses. This deployment differs from a physical in-path deployment in that a packet
redirection mechanism is used to direct packets to Steelhead appliances that are not in the
physical path of the client or server.
Commonly used technologies for redirection are: Layer-4 switches, Web Cache Communication
Protocol (WCCP), and Policy-based Routing (PBR).
Server-Side Out-of-Path
A server-side out-of-path deployment is a network configuration in which the Steelhead
appliance is not in the direct or logical path between the client and the server. Instead, the server-
side Steelhead appliance is connected through the Primary interface and listens on port 7810 to
connections coming from client-side Steelhead appliances. In an out-of-path deployment, the
Steelhead appliance acts as a proxy and does not perform NAT of the client’s IP address as with
in-path deployments (to allow the server to see the original client IP address), but will instead
source NAT to the Primary interface address on the Steelhead appliance that is in server-side
out-of-path. A server-side out-of-path configuration is suitable for data center locations when
physical in-path or logical in-path configurations are not possible. With server-side out-of-path,
client IP visibility is no longer available to the server (due to the NAT) and optimization initiated
from the server side is not possible (since there is no redirection of the outbound connection’s
packets to the Steelhead appliance).
Physical Device Cabling
Steelhead appliances have multiple physical and virtual interfaces. The Primary interface is
typically used for management purposes, data store synchronization (if applicable), and for
server-side out-of-path configurations. The Primary interface can be assigned an IP address and
connected to a switch. You would use a straight-through cable for this configuration.
The LAN and WAN interfaces are purely L1/L2. No IP addresses can be assigned. Instead, a
logical L3 interface is created. This is the “In-path” interface and it is designated a name on a per
slot and port basis (in LAN/WAN pairs). A bypass card (or in-path card) in slot0 with just one
LAN and one WAN interface will have a logical interface called inpath0_0. In-path interfaces
for a 4-port card in slot1 will get inpath1_0 and inpath1_1, representing the pair or LAN/WAN
ports respectively.
Inpath1_0 will represent LAN1_0 and WAN1_0. Inpath1_1 will represent LAN1_1 and
WAN1_1.


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For a physical in-path deployment, when connecting the LAN and WAN interface to the
network, both of them are to be treated as a router. When connecting to a router, host, or firewall,
a crossover cable needs to be used. When connecting to a switch, a straight-through cable has to
be used. The Steelhead appliance supports auto-MDIX (medium dependent interface crossover),
however when using the wrong cables you run the risk of breaking the connection between the
components the Steelhead appliances placed in-between, especially in bypass. These components
may not support auto-MDIX.
For a virtual in-path deployment the WAN interface needs to be connected. The LAN interface
does not need to be connected and will be shut down automatically as soon as the virtual in-path
option is enabled in the Steelhead appliances configuration.
For server-side out-of-path deployments only the Primary interface needs to be connected.
In-path
In-path Networks
Physical in-path configurations are suitable for locations where the total bandwidth is within the
limits of the installed Steelhead appliance or serial cluster of Steelhead appliances.
The Steelhead appliance can be physically connected to access both ports and trunks. When the
Steelhead appliance is placed on a trunk, the In-path interface has to be able to tag its traffic with
the correct VLAN number. The supported trunking protocol is 802.1q (“Dot1Q”). A tag can be
assigned via the GUI or the CLI. The CLI command for this is:
HOSTNAME (config) # in-path interface inpathx_x vlan <id>
Inter-Steelhead appliance traffic will use this VLAN (except in Full Transparent connections as
explained below).
There are several variations of the in-path deployment. Steelhead appliances could be placed in
series to be redundant. Peering rules based on a peer IP address will have to be applied to both
Steelhead appliances to avoid peering between each other. When using 4-port cards, and thus
multiple in-path IP addresses, all addresses will have to be defined to avoid peering.
A serial cluster is a failover design that can be used to mitigate the risk of possible network
instabilities and outages caused by a single Steelhead appliance failure (typically caused by
excessive bandwidth as there is no longer data reduction occurring). When the maximum number
of TCP connections for a Steelhead appliance is reached, that appliance stops intercepting new
connections. This allows the next Steelhead appliance in the cluster the opportunity to intercept
the new connections, if it has not reached its maximum number of connections. The in-path
peering rules and in-path rules are used so that the Steelhead appliances in the cluster know not
to intercept connections between themselves.
Appliances in a failover deployment process the peering rules you specify in a spill-over fashion.
A keepalive method is used between two Steelhead appliances to monitor each others status and
set a master and backup state for both Steelhead appliances. It is recommended to assign the
LAN-side Steelhead appliance to be the master due to the amount of passthrough traffic from
Steelhead to client or server. Optionally, data stores can be synchronized to ensure warm
performance in case of a failure.
In case the Steelhead appliances are deployed in parallel of each other, measures need to be
taken to avoid asymmetrical traffic from being passed through without optimization. This usually
occurs when two or more routing points in the network exist where traffic is spread over the
links simultaneously. Connection Forwarding can be used to exchange flow information between


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the Steelhead appliances in the parallel deployment. Multiple Steelhead appliances can be
bundled together.
WAN Visibility Modes
WAN visibility pertains to how packets traversing the WAN are addressed. RiOS v5.0 offers
three types of WAN visibility modes: correct addressing, port transparency, and full address
transparency.
You configure WAN visibility on the client-side Steelhead appliance (where the connection is
initiated). The server-side Steelhead appliance must also support multiple WAN visibility (RiOS
v5.0 or later).
Correct Addressing
Correct addressing uses Steelhead appliance IP addresses and port numbers in the TCP/IP packet
header fields for optimized traffic in both directions across the WAN. This is the default setting.
This is “correct” as the devices which are communicating (the TCP endpoints) are the Steelhead
appliances, so their IP addresses/ports are reflected in the connection.
Port Transparency
Port address transparency preserves your server port numbers in the TCP/IP header fields for
optimized traffic in both directions across the WAN. Traffic is optimized while the server port
number in the TCP/IP header field appears to be unchanged. Routers and network monitoring
devices deployed in the WAN segment between the communicating Steelhead appliances can
view these preserved fields. Use port transparency if you want to manage and enforce QoS
policies that are based on destination ports. If your WAN router is following traffic classification
rules written in terms of client and network addresses, port transparency enables your routers to
use existing rules to classify the traffic without any changes. Port transparency enables network
analyzers deployed within the WAN (between the Steelhead appliances) to monitor network
activity and to capture statistics for reporting by inspecting traffic according to its original TCP
port number. Port transparency does not require dedicated port configurations on your Steelhead
appliances.
NOTE: Port transparency only provides server port visibility. It does not provide client and
server IP address visibility, nor does it provide client port visibility.
Full Transparency
Full address transparency preserves your client and server IP addresses and port numbers in the
TCP/IP header fields for optimized traffic in both directions across the WAN. It also preserves
VLAN tags. Traffic is optimized while these TCP/IP header fields appear to be unchanged.
Routers and network monitoring devices deployed in the WAN segment between the
communicating Steelhead appliances can view these preserved fields. If both port transparency
and full address transparency are acceptable solutions, port transparency is preferable. Port
transparency avoids potential networking risks that are inherent to enabling full address
transparency. For details, see the Steelhead Appliance Deployment Guide. However, if you must
see your client or server IP addresses across the WAN, full transparency is your only
configuration option.
Out-of-Band (OOB) Splice
What is the OOB Splice?
An OOB splice is an independent, separate TCP connection made on the first connection
between two peer Steelhead appliances used to transfer version, licensing and other OOB data
between peer Steelhead appliances. An OOB connection must exist between two peers for

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connections between these peers to be optimized. If the OOB splice dies all optimized
connections on the peer Steelhead appliances will be terminated.
The OOB connection is a single connection existing between two Steelhead appliances
regardless of the direction of flow. So if you open one or more connections in one direction, then
initiate a connection from the other direction, there will still be only one connection for the OOB
splice. This connection is made on the first connection between two peer Steelhead appliances
using their in-path IP addresses and port 7800 by default. The OOB splice is rarely of any
concern except in full transparency deployments.
Case Study
In the example below, the Client is trying to establish connection to Server-1:
SFE-2 Server-2
10.3.0.2 10.3.0.10
Server-1
10.2.0.10

10.3.0.1

10.1.0.1 1.1.1.1 2.2.2.2 10.2.0.1
WAN

Client CFE-1 FW-1 FW-2 SFE-1
10.1.0.10 10.1.0.2 10.2.0.2

Issue 1: After establishing inner connection, the Client will try to establish an OOB connection
to the Server-B. It will address it by the IP address reported by Steelhead (SFE-1) which is in
probe response (10.2.0.2). Clearly, the connection to this address will fail since 10.2.x.x
addresses are invalid outside of the firewall (FW-2).
Resolution 1: In the above example, there is one combination of address and port (IP:port) we
know about, the connection the client is destined for which is Server-1. The client should be able
to connect to Server-1. Therefore, the OOB splice creation code in sport can be changed to create
a transparent OOB connection from the Client to Server-1 if the corresponding inner connection
is transparent.
How to Configure
There are three options to address the problem of the OOB splice connection established
mentioned in Issue 1 above.
In a default configuration the out-of-band connection uses the IP addresses of the client-side
Steelhead and server-side Steelhead. This is known as correct addressing and is our default
behavior. However, this configuration will fail in the network topology described above but
works for the majority of networks. The command below is the default setting in a Steelhead
appliance’s configuration.
in-path peering oobtransparency mode none
In the network topology discussed in Issue 1, the default configuration does not work. There are
two oobtransparency modes that may work in establishing the peer connections; destination and
full. When destination mode is used, the client uses the first server IP and port pair to go through
the Steelhead appliance with which to connect to the server-side Steelhead appliance and the
client-side Steelhead IP and port number chosen by the client-side Steelhead appliance. To
change to this configuration use the following CLI command:


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in-path peering oobtransparency mode destination
In oobtransparency full mode, the IP of the first client is used and a pre-configured on the client-
side Steelhead appliance to use port 708. The destination IP and port are the same as in
destination mode, i.e., that of the server. This is the recommended configuration when VLAN
transparency is required. To change to this configuration use the following CLI command:
in-path peering oobtransparency mode full
To change the default port used the by the client-side Steelhead appliance when
oobtransparency mode full is configured, use the following CLI command:
in-path peering oobtransparency port
It is important to note that these oobtransparency options are only used with full transparency. If
the first inner-connection to a Steelhead was not transparent, the OOB will always use correct
addressing.
Virtual In-path
Introduction to Virtual In-path Deployments
In a virtual in-path deployment, the Steelhead appliance is virtually in the path between clients
and servers. Traffic moves in and out of the same WAN interface. This deployment differs from
a physical in-path deployment in that a packet redirection mechanism is used to direct packets to
Steelhead appliances that are not in the physical path of the client or server.
Redirection mechanisms:
• Layer-4 Switch. You enable Layer-4 switch (or server load-balancer) support when you
have multiple Steelhead appliances in your network to manage large bandwidth
requirements.
• PBR (Policy-Based Routing). PBR enables you to redirect traffic to a Steelhead appliance
that is configured as virtual in-path device. PBR allows you to define policies to redirect
packets instead of relying on routing protocols. You define policies to redirect traffic to the
Steelhead appliance and policies to avoid loop-back.
• WCCP (Web Cache Communication Protocol). WCCP was originally implemented on
Cisco routers, multi-layer switches, and web caches to redirect HTTP requests to local web
caches (version 1). Version 2, which is supported on Steelhead appliances, can redirect any
type of connection from multiple routers or web caches and different ports.
Policy-Based Routing (PBR)
Introduction to PBR
PBR is a router configuration that allows you to define policies to route packets instead of
relying on routing protocols. It is enabled on an interface basis and packets coming into a PBR-
enabled interface are checked to see if they match the defined policies. If they do match, the
packets are routed according to the rule defined for the policy. If they do not match, packets are
routed based on the usual routing table. The rules can redirect the packets to a specific IP
address.
To avoid an infinite loop, PBR must be enabled on the interfaces where the client traffic is
arriving and disabled on the interfaces corresponding to the Steelhead appliance. The common
best practice is to place the Steelhead appliance on a separate subnet.
One of the major issues with PBR is that it can black hole traffic (drop all TCP connections to a
destination) if the device it is redirecting to fails. To avoid black holing traffic, PBR must have a


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way of tracking whether the PBR next hop is available. You can enable this tracking feature in a
route map with the following Cisco router command:
set ip next-hop verify-availability
With this command, PBR attempts to verify the availability of the next hop using information
from CDP. If that next hop is unavailable, it skips the actions specified in the route map. PBR
checks availability in the following manner:
1. When PBR first attempts to send to a PBR next hop, it checks the CDP neighbor table to see
if the IP address of the next hop appears to be available. If so, it sends an Address Resolution
Protocol (ARP) request for the address, resolves it, and begins redirecting traffic to the next
hop (the Steelhead appliance).
2. After PBR has verified the next hop, it continues to send to the next hop as long as it obtains
answers from the ARP request for the next hop IP address. If the ARP request fails to obtain
an answer, it then rechecks the CDP table. If there is no entry in the CDP table, it no longer
uses the route map to send traffic. This verification provides a failover mechanism.
In more recent versions of the Cisco IOS software, there is a feature called PBR with Multiple
Tracking Options. In addition to the old method of using CDP information, it allows methods
such as HTTP and ping to be used to determine whether the PBR next hop is available. Using
CDP allows you to run with older IOS 12.x versions.
WCCP Deployments
Introduction to WCCP
The WCCP protocol is a stateful language that the router and Steelhead appliance can use to
redirect traffic to the Steelhead appliance in order for it to optimize. Several functions will have
to be covered to make it stateful and scalable. Failover, load distribution, and negotiation of
connection parameters will all have to be communicated throughout the cluster that the Steelhead
appliance and router form upon successful negotiation. The protocol has four messages to
encompass all of the above functions:
• HERE_I_AM. Sent by Steelhead appliances to announce themselves.
• I_SEE_YOU. Sent by WCCP enabled routers to respond to announcements.
• REDIRECT_ASSIGN. Sent by the designated Steelhead appliance to determine flow
distribution.
• REMOVAL_QUERY. Sent by router to check a Steelhead appliance after missed
HERE_I_AM messages.
When you configure WCCP on a Steelhead appliance:
• Routers and Steelhead appliances are added to the same service group.
• Steelhead appliances announce themselves to the routers.
• Routers respond with their view of the service group.
• One Steelhead will be the designated CE (caching engine) and tells the routers how to
redirect traffic among the Steelhead appliances in the service group.
How Steelhead Appliances Communicate with Routers
Steelhead appliances can use one of the following methods to communicate with routers:
• Unicast UDP. The Steelhead appliance is configured with the IP address of each router. If
additional routers are added to the service group, they must be added on each Steelhead
appliance.
• Multicast UDP. The Steelhead appliance is configured with a multicast group. If additional
routers are added, you do not need to add or change configuration settings on the Steelhead
appliances.


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Redirection
By default, all TCP traffic is redirected, optionally a redirect-list can be defined where only the
contents of the redirect-list are redirected. A redirect-list in a WCCP configuration refers to an
ACL that is configured on the router to select the traffic that will be redirected.
Traffic is redirected using one of the following schemes:
• GRE (Generic Routing Encapsulation). Each data packet is encapsulated in a GRE packet
with the Steelhead appliance IP address configured as the destination. This scheme is
applicable to any network.
• L2 (Layer 2). Each packet MAC address is rewritten with a Steelhead appliance MAC
address. This scheme is possible only if the Steelhead appliance is connected to a router at
Layer 2.
• Either. The either value uses L2 first—if Layer 2 is not supported, GRE is used. This is the
default setting.
You can configure your Steelhead appliance to not encapsulate return packets. This allows your
WCCP Steelhead appliance to negotiate with the router or switch as it if were going to send gre-
return packets, but to actually send l2-return packets. This configuration is optional but
recommended when connected at L2 directly. The command to override WCCP packet return
negotiation is wccp l2-return enable. Be sure the network design permits this.
Load Balancing and Failover
WCCP supports unequal load balancing. Traffic is redirected based on a hashing scheme and the
weight of the Steelhead appliances. Each router uses a 256-bucket Redirection Hash Table to
distribute traffic for a Service Group across the member Steelhead appliances. It is the
responsibility of the Service Group's designated Steelhead appliance to assign each router's
Redirection Hash Table. The designated Steelhead appliance uses a
WCCP2_REDIRECT_ASSIGNMENT message to assign the routers' Redirection Hash Tables.
This message is generated following a change in Service Group membership and is sent to the
same set of addresses to which the Steelhead appliance sends WCCP2_HERE_I_AM messages.
A router will flush its Redirection Hash Table if a WCCP2_REDIRECT_ASSIGNMENT is not
received within five HERE_I_AM_T seconds of a Service Group membership change. The
HASH algorithm can use several different input fields to come up with an 8 bit output (which is
the bucket value). Default input fields are source and destination IP address of the packet that is
redirected. Source and destination TCP port or any combination can be used.
The weight determines the percentage of traffic a Steelhead appliance in a cluster gets, the
hashing algorithm determines which flow is redirected to which Steelhead appliance. The default
weight is based on the Steelhead appliance model number. The weight is heavier for models that
support more connections. You can modify the default weight if desired.
With the use of weight you can also create an active/passive cluster by assigning a weight of 0 to
the passive Steelhead appliance. This Steelhead appliance will only get traffic when the active
Steelhead appliance fails.
Assignment and Redirection Methods
The assignment method refers to how a router chooses which Steelhead appliance in a WCCP
service group to redirect packets to. There are two assignment methods: the Hash assignment
method and the Mask assignment method. Steelhead appliances support both the Hash
assignment and Mask assignment methods.
HASH


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Redirection using Hash assignment is a two-stage process. In the first stage a primary key is
formed from the packet which is defined by the Service Group and is hashed to yield an index.
This index number will then be placed into a Redirection Hash Table.
In the Redirection Hash Table a packet has either an unflagged web-cache, unassigned bucket, or
a flagged packet. In the event the packet has an unflagged web-cache, the packet is redirected to
that web-cache. If the bucket is unassigned the packet is forwarded normally. However, if the
bucket is flagged indicating a secondary hash then a secondary key is formed (as defined by the
Service Group description). This key is hashed to yield an index number which in turn is placed
into the Redirection Hash Table. If this secondary entry contains a web-cache index then the
packet is directed to that web-cache. If the entry is unassigned the packet is forwarded normally.
MASK
The first phase of Mask assignment is defining the mask itself. The mask can be up to seven bits
and can be applied to the SRC TCP port, DST TCP port, source IP address or DST IP address or
a combination of the four attributes but may not exceed seven bits. Depending on the amount of
bits selected different number of buckets are created and assigned to the different Steelhead
appliances in the service group. As traffic traverses the router a bitwise AND operation is
performed between the mask and the IP address/TCP port depending on the mask defined. The
traffic is assigned to the different buckets based on the results of the AND operation.
Mask IP address/TCP port pairs are processed in an order they are received and in turn are
compared to the seven bits.
From Internet-Draft WCCP version 2 (http://www.wrec.org/Drafts/draft-wilson-wrec-wccp-v2-
00.txt ):
Note that in all of the mask fields of this element a zero means "Don't care”.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Address Mask |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Address Mask |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Port Mask | Destination Port Mask |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

• Source Address Mask. The 32-bit mask to be applied to the source IP address of the packet.
• Destination Address Mask. The 32-bit mask to be applied to the destination IP address of
the packet.
• Source Port Mask. The 16-bit mask to be applied to the TCP/UDP source port field of the
packet.
• Destination Port Mask. The 16-bit mask to be applied to the TCP/UDP destination port
field of the packet.
It may not be obvious for the details here but there is a priority bit order when using Mask. The
above diagram reads from most significant to least significant bottom left to top. In other words,
the priority bits will be source port, destination port, destination address, and source address.
This is helpful in knowing in the event of troubleshooting which bucket a specific resource is
allocated.


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For more information regarding Hash or Mask assignment, refer to the Steelhead Appliance
Deployment Guide and the whitepaper “WCCP Mask Assignment” provided on the Riverbed
Partner Portal and/or Riverbed Technical Support site.
Advanced WCCP Configuration
Using Multicast Groups
If you add multiple routers and Steelhead appliances to a service group, you can configure them
to exchange WCCP protocol messages through a multicast group. Configuring a multicast group
is advantageous because if a new router is added, it does not need to be explicitly added on each
Steelhead appliance.
Multicast addresses must be between 224.0.0.0 and 239.255.255.255.
Configuring Multicast Groups on the Router
On the router, at the system prompt, enter the following set of commands:
Router> enable
Router# configure terminal
Router(config)# ip wccp 90 group-address 224.0.0.3
Router(config)# interface fastEthernet 0/0
Router(config-if)# ip wccp 90 redirect in
Router(config-if)# ip wccp 90 group-listen
Router(config-if)# end
Router# write memory
NOTE: Multicast addresses must be between 224.0.0.0 and 239.255.255.255.
Configuring Multicast Groups on the Steelhead Appliance
On the WCCP Steelhead appliance, at the system prompt, enter the following set of commands:
WCCP Steelhead > enable
WCCP Steelhead # configure terminal
WCCP Steelhead (config) # wccp enable
WCCP Steelhead (config) # wccp mcast-ttl 10
WCCP Steelhead (config) # wccp service-group 90 routers 224.0.0.3
WCCP Steelhead (config) # write memory
WCCP Steelhead (config) # exit
Limiting Redirection by TCP Port
By default all TCP ports are redirected, but you can configure the WCCP Steelhead appliance to
tell the router to redirect only certain TCP source or destination ports. You can specify up to a
maximum of seven ports per service group.
Using Access Lists for Specific Traffic Redirection
If redirection is based on traffic characteristics other than ports, you can use ACLs on the router
to define what traffic is redirected.
ACL considerations:
• ACLs are processed in order, from top to bottom. As soon as a particular packet matches a
statement, it is processed according to that statement and the packet is not evaluated against
subsequent statements. Therefore, the order of your access-list statements is very important.


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• If no port information is explicitly defined, all ports are assumed.
• By default all lists include an implied deny all entry at the end, which ensures that traffic that
is not explicitly included is denied. You cannot change or delete this implied entry.
Access Lists: Best Practice
To avoid requiring the router to do extra work, Riverbed recommends that you create an ACL
that routes only TCP traffic to the Steelhead appliance. When a WCCP configured Steelhead
appliance receives UDP, GRE, ICMP, and other non-TCP traffic, it returns the traffic to the
router.
Verifying and Troubleshooting WCCP Configuration
Checking the Router Configuration
Router>en
Router#show ip wccp
Router#show ip wccp 90 detail
Router#show ip wccp 90 view
Verifying WCCP Configuration on an Interface
Router>en
Router#show ip interface
Look for WCCP status messages near the end of the output.
You can trace WCCP packets and events on the router.
Checking the Access List Configuration
Router>en
Router#show access-lists <access_list_number>
Tracing WCCP Packets and Events on the Router
Router>en
Router#debug ip wccp events
WCCP events debugging is on
Router#debug ip wccp packets
WCCP packet info debugging is on
Router#term mon

Server-Side Out-of-Path Deployments
Out-of-path Networks
An out-of-path deployment is a network configuration in which the Steelhead appliance is not in
the direct physical or logical path between the client and the server. In an out-of-path
deployment, the Steelhead appliance acts as a proxy. An out-of-path configuration is suitable for
data center locations where physical in-path or virtual in-path configurations are not possible.


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In an out-of-path deployment, the client-side Steelhead appliance is configured as an in-path
device, and the server-side Steelhead appliance is configured as an out-of-path device.
The command to enable server-side out-of-path is:
HOSTNAME (config) # out-of-path enable

LAN I/F WAN I/F
WAN
Client-side PRI IP SRC=S-SH
Steelhead
Fixed-target Rule

Server-side
Steelhead

A fixed-target rule is applied on the client-side Steelhead appliance to make sure the TCP session
is intercepted and statically sent to the out-of-path Steelhead appliance on the server side. When
enabling out-of-path on the server-side Steelhead appliance, it starts listening on port 7810 for
incoming connections from a client-side Steelhead appliance.
The Steelhead appliance can perform NAT. The server will see the IP address of the Steelhead
appliance as the source of the connection so the packets are returned to the Steelhead appliance
instead of the client. This is necessary to make sure that the bidirectional traffic is seen by the
Steelhead appliance. Also keep in mind that optimization will only occur when the TCP
connection is initiated by the client.
Out-of-Path, Failover Deployment
An out-of-path, failover deployment serves networks where an in-path deployment is not an
option. This deployment is cost effective, simple to manage, and provides redundancy.
When both Steelhead appliances are functioning properly, the connections traverse the master
appliance. If the master Steelhead appliance fails, subsequent connections traverse the backup
Steelhead appliance. When the master Steelhead appliance is restored, the next connection
traverses the master Steelhead appliance. If both Steelhead appliances fail, the connection is
passed through unoptimized to the server. The way to do this is to specify multiple target
appliances in the fixed-target in-path rule on the client-side Steelhead appliance.


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Data Center LAN

Switch

Server
WAN
Router

Steelhead A

Steelhead B

Hybrid Mode: In-Path and Server-Side Out-of-Path Deployment
A hybrid mode deployment serves offices with one WAN routing point and users, and where the
Steelhead appliance must be referenced from remote sites as an out-of-path device (for example,
to avoid mistaken auto-discovery or to bypass intermediary Steelhead appliances).
The following figure illustrates the client-side of the network where the Steelhead appliance is
configured as both an in-path and server-side out-of-path device.

Steelhead Firewall/VPN
Switch
WAN
PRI
DMZ

Client FTP Server Web Server

In this hybrid design, a client-side Steelhead appliance (not shown) would use a typical auto-
discovery process to optimize any data going to or coming from the clients shown. If however, a
remote user would like to get optimization to the DMZ shown above, the standard auto-
discovery process would not function properly since the packet flow would prevent the auto-
discovery probe from ever reaching the Steelhead appliance. To remedy this, a fixed-target rule
matching the destination address of the DMZ and targeted to the Primary (PRI) interface of the
Steelhead appliance above will ensure that the traffic will reach the Steelhead appliance, and due
to the server-side out-of-path NAT process, will ensure that it returns to the Steelhead appliance
for optimization on the return path.
Asymmetric Route Detection
Asymmetric auto-detection enables Steelhead appliances to detect the presence of asymmetry
within the network. Asymmetry is detected by the client-side Steelhead appliances. Once
detected, the Steelhead appliance will pass through asymmetric traffic unoptimized allowing the
TCP connections to continue to work. The first TCP connection for a pair of addresses might be


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