Bgp 1232073634451868-3

Introduction to
Border Gateway Protocol
(BGP 4)

Version 1.2

Summary
 BGP Concept

 BGP Operation

 Route Control

 Configuration

 Trouble-shooting

 Juniper vs. Cisco

Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 2

Summary
 BGP Concept

 BGP Operation

 Route Control

 Configuration




Concepts
 The BGP protocol was developed by the IDR Working Group
of IETF. A first version of BGP was published in June 1989
as RFC 1105 (BGP-1). A second version was published in
June 1990 as RFC 1163 (BGP-2). A third version was
published in October 1991 as RFC 1267 (BGP-3).
 A fourth version was published in July 1994 as RFC 1654
(BGP-4). The Current version of BGP-4 is documented in
RFC 1771 (March 1995).
 BGP-4 supports
 the path vector concept to avoid the potential routing loop introduced by
complicated (I.e., full-meshed) Internet topology
 IP prefix and length advertisements


BGP Protocol Overview
 JUNOS software supports BGP Version 4 and several extensions to
the protocol
 RFC 1771, A Border Gateway Protocol 4 (BGP-4)
 RFC 1772, Application of the Border Gateway Protocol in the Internet
 RFC 1965, Autonomous System Confederations for BGP
 RFC 1966, BGP Route Reflection: An Alternative to Full-Mesh IBGP
 RFC 1997, BGP Communities Attribute
 RFC 2270, Using a Dedicated AS for Sites Homed to a Single Provider
 RFC 2283, Multiprotocol Extensions for BGP-4
 RFC 2385, Protection of BGP Sessions via the TCP MD5 Signature
Option
 RFC 2439, BGP Route Flap Damping
 Capabilities Negotiation with BGP4, IETF draft draft-ietf-idr-cap-neg-01
 BGP Extended Communities Attribute, IETF draft-ramachandra-bgp-
ext-communities-04.txt


Concepts
 the concept of classless interdomain routing to allow better use of
existing IP address space and to minimize the rapid growth of
routing table size (CIDR, RFC 1519)
 policy-based routing using a set of pre-defined path attributes
 BGP-4 supports route aggregation and AS aggregation (I.e., AS
Set and Confederation)
 fast convergence by requiring the router to inform its neighbors
when the previously announced routes become unreachable
 large routing table size
 authentication using BGP identifier and AS number. In addition, it
supports encrypted signature in every BGP message.


Concepts
 BGP routers only use those routes whose next-hop can be reached
 BGP routers advertise only those routes that they use
 BGP runs over a reliable transport protocol.
 TCP port 179
 takes care of segmenting, sequencing, retransmission and
acknowledgments
 supports a "graceful" close, i.e., that all outstanding data will be
delivered before the connection is close.
 - 4096 max frame size
 - hold time (90 sec def – smallest used between peers)
 - open->updates->keepalives (steady state)-> notification
(close)
 | |
 ------ --- -------
 BGP MIB consists of the BGP Peer Table, The BGP Path Attribute
Table and a Global Table.


Concepts
Autonomous System (AS)
 The classic definition of an Autonomous System is a set of routers
under a single technical administration, using a single IGP and
common metrics to route packets within the AS, and using an EGP
to route packets to other ASs.
 Currently, it has become common for a single AS to use several
IGPs and sometimes several sets of metrics within an AS.
 The use of the term Autonomous System here stresses the fact that,
even when multiple IGPs and metrics are used, the administration
of an AS appears to other ASs to have a single coherent interior
routing plan and presents a consistent picture of what
destinations are reachable through it.


Concepts
Autonomous System Type
• Stub AS BGP Peers
Provider "B"
– Single Exit Point
Provider "A"
– Local Traffic Transit AS
AS 60
• Multi-Homed AS Transit AS
– Multiple Exit Points
– Local Traffic AS 50

•Transit AS TCP Connections Customer #1
– Local and Transit Traffic AS 100
Stub As
Stub As
Customer #n
AS 120
Multi-Homed
EBGP Customer #2
IBGP AS 110


BGP AS
 What is an AS?
 - 16 bit integer (1-65535)
 - 64512-65535 private.


Concepts
CIDR = Classless Inter Domain Routing
 Address Assignment and Aggregation Strategy
A mechanism to aggregate IP addresses into blocks of
multiple of the old style classes of addresses
 Reduces routing information through this aggregation
 Conserves Resources
 router resources (CPU, memory)
 bandwidth (less routes -> less routing packets)


Concepts
 Supernet
 Organizations are allocated Blocks of IP addresses

 These blocks are allocated in powers of 2

 The Blocks of Address Space can be Aggregated into one
routing announcement (Supernetting)
 Block of 256 “Class C” Networks (or a class B sized block)
 IP addresses 192.24.0.0 thru 192.24.255.255
 Can be described by one Supernetted Route
192.24.0.0 Mask 255.255.0.0


Concepts
Exterior Routes

Routes learned from other autonomous
systems


Concepts
External Neighbor
 Between BGP Speakers in
different AS
 Should be directly connected AS 100
 Configuration
Router A A
bgp { .1
group EXTERNAL { 1.1.1.0
neighbor 1.1.1.2;
type external; AS 200
peer-as 200 ;
}
{ .2 B
Router B
bgp {
group EXTERNAL {
neighbor 1.1.1.1;
type external;
peer-as 100 ;
}
{


Concepts
Internal Neighbor
 Neighbor in same AS
 May be several hop away
 Configuration
Router A
bgp { AS 100
group INTERNAL {
type internal;
neighbor 1.1.1.1; A
}
}
B

Router B
bgp {
group INTERNAL {
neighbor 2.2.2.2;
type internal;
}
{


Concepts
Internal vs. External BGP
IBGP Update EBGP Update
 Local Preference Preserved Removed
 MED Preserved Removed the MED from
previous AS
 Cluster list Prepend the Cluster ID Unchanged
by RR
 Next-hop address Preserved Changed to the local address
 AS Path Unchanged Prepend the local AS


BGP Attribute
Well-known mandatory – Always present in a BGP update. All
BGP implementations recognize these attributes. An example
is the BGP next hop attribute. (Origin, AsPath)
Well-known discretionary - Might be present in a BGP update.
All BGP implementations recognize these attributes. An
example is the local preference attribute.
Optional transitive - Must be passed to other BGP peers even if
the local peer does not understand or process the attribute.
An example is the community attribute.
Optional non-transitive - Must not be passed to other BGP
peers. An example is the MED attribute


Concepts
AS path Attributes
 Standard attribute types
 1, ORIGIN (well-known mandatory)
 2, AS_PATH (well-known mandatory)
 3, NEXT_HOP (well-known mandatory)
 4, MULTI_EXIT_DISC (optional non-transitive)
 5, LOCAL_PREF (well-known discretionary)
 6, ATOMIC_AGGREGATE (well-known discretionary)
 7, AGGREGATOR (optional transitive)

 Additional attribute types have been created via supplemental
specifications to extend the protocol
 8, Community (optional transitive)
 9, Originator Id (optional non-transitive)
 10, Cluster list (optional non-transitive)
 11, Destination Path Attribute (optional transitive)


Concepts
AS-Path
 Path traversed one or more
members of a set
{100 200} (as-set) 100
143.89.14.0/24
206.161.46.0/24
 A list of AS’s that a route has 200
206.161.47.0/24
traversed
300 100 (sequence)
300
210.168.35.0/24

143.89.14.0/24 300 100
210.168.35.0/24 300
206.161.46.0/23 300 {100 200}


Concepts
Next-hop
set by EBGP speaker or policy

 Next hop to reach a network
 Router A will advertise 100.100.100.1 next hop for network 150.10.0.0

A AS 109
150.10.0.0/16
100.100.100.0
.1

.2
AS 173
B


Concepts
Next-hop Issue
 Router B would advertise 100.100.100.3 as an “next-hop” to reach the
network behind router C to AS 109 ( router A )
Router A

AS 109

.1
EBGP
100.100.100.0/24

.2 .3

AS 173

Router B Router C


Concepts
Next-hop Issue
 Problem will occur if the network in-between is actually an NBMA
network !
Router A

AS 109

.1
EBGP
100.100.100.0/24

.2 .3

AS 173

Router B Router C


Concepts
Next-hop Issue
 Use “next-hop self” to solve
Router B: Router A
protocol bgp {
AS 109
group BGP-to-router-A {
export chg-nexthop; .1
} EBGP
} 100.100.100.0/24
policy-options policy-statement chg-nexthop {
from protocol bgp; .2 .3
then next-hop self;
AS 173
}
Router B Router C


Concepts
Local Preference
AS 200
AS 666

AS 180

Where to 200 ??

AS 173

 Preference send to all routers in local AS
 Path with highest preference value are most desirable


Concepts
Local Preference
AS 200
AS 666

AS 180

bgp {
group EXTERNAL { AS 173
type external;
peer-as 666
local-preference 100;
neighbor 1.1.1.1;
}
}


Concepts

Multi-Exit Discriminator (MED)
32-bit, non-negative

 Affects all routes from same AS path
 Advertised to external neighbors
 Lower MED value is more preferable


Concepts
AS 666 AS 200

AS 1800
AS 1988
AS 2000
AS 173

 Applies on a AS path basis


Concepts
Router A:
bgp {
group EXTERNAL {
type external;
neighbor 1.1.1.1 {
export MED; policy-statement MED {
peer-as 666; from as-path via-200;
} then {
} metric 200;
} accept;
}
}
as-path via-200 ".* 200";


Concepts

AS 666 set MED = 200 AS 200

A

AS 1800
AS 1988
AS 2000
AS 173


Concepts
Origin
 describes how a route was injected into BGP at the originating AS
 IGP
Default export type on policy statement for BGP

 EGP
From protocol EGP, can be specified in the export policy

 Incomplete
Unknown source of information, can be specified in the export
policy


Concepts
Atomic Aggregate
 Used to inform BGP speaker about less specific
route.

 More specific route exists and is included in it

 BGP speaker receiving this attribute shall not
remove the attribute when propagating it


Concepts
Aggregator (6-bytes)

Last AS number that formed the aggregate
route (2 bytes)

IP address of the BGP speaker that formed
the aggregate route (4-bytes)


Concepts
Route Reflector and Confederation

 Scaling would be an issue when there are too many BGP
peer within the AS
 BGP speaker would not pass the BGP routes learn from
an IBGP peer to another IBGP peers
 Number of connection required = n(n-1)/2


Concepts
Route Reflector – RFC 1966
 Acting as a “mirror” to reflect the BGP routes learned
from the IBGP peers to the clients
 Update from non-client to all clients
 Update from client to all non-clients and the other clients
except the one originated the route
 Provide the normal BGP speaker function to all other
non-clients
 Pending cluster-list and originator ID


Concepts
Route Reflector
IBGP AS300

EBGP EBGP

IBGP

IBGP
IBGP IBGP
AS100 AS200
IBGP

IBGP

IBGP AS300
RR
EBGP EBGP

non-client
IBGP
AS100 AS200
IBGP

client client


Concepts
Route Reflector
 Loop Prevention
 Originator ID
If the attribute “originator ID” has not been created in the
attribute of the route, the RR will create this attribute

The content of “originator ID” is the router ID of the IBGP peer
that pass this route to the RR

The RR would not reflect the route back to the
originator


Concepts
Route Reflector
 Loop Prevention
 Cluster list
When the RR reflect the route to other peers, it will prepend it’s
cluster ID within the cluster list

If the RR receive a route with it’s cluster ID within the
cluster list, the route would be discarded


Concepts
Confederation – RFC 1965

 Scale down an AS into several Sub-ASs
 Each BGP peers between sub-AS would act as EBGP peer
except some of the attributes remain unchanged
 Local-preference passed through such a connect
 MED, next-hop unchanged between member AS’s of the
confederation.


Concepts
Confederation
IBGP
IBGP

EBGP

IBGP
IBGP
IBGP
IBGP
AS100
IBGP

IBGP IBGP EBGP

AS200 EBGP

AS65500
IBGP
IBGP
IBGP
IBGP
AS100
IBGP

AS65501
AS200


Summary
 BGP Concept

 BGP Operation

 Route Control

 Configuration




BGP Protocol Messages
 Four types of messages
 Open
 Update
 Keepalive
 Notification


BGP Header
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ +
| Marker |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

•Marker: synchronization and authentication


BGP Open message

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
+-+-+-+-+-+-+-+-+
| Version |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| My Autonomous System |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Hold Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BGP Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opt Parm Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Optional Parameters |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


OPEN Message (Cont.)

Optional Parameters
 Authentication Information (type 1)

0 1 2 3 4 5 6 7 8
+-+-+-+-+-+-+-+-+
| Auth. Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Authentication Data |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


NOTIFICATION Message
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error code | Error subcode | Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

1 = HRD Error
2 = OPEN Error
3= UPDATE Error
4 = Hold Time Expired
5 = FSM Error
6 = Cease(for fatal errors besides the ones already listed)


UPDATE Message
+-----------------------------------------------------+
| Unfeasible Routes Length (2 octets) |
+-----------------------------------------------------+
| Withdrawn Routes (variable) |
+-----------------------------------------------------+
| Total Path Attribute Length (2 octets) |
+-----------------------------------------------------+
| Path Attributes (variable) |
+-----------------------------------------------------+
| Network Layer Reachability Information (variable) |
+-----------------------------------------------------+

0 1 +---------------------------+
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 | Length (1 octet) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +---------------------------+
| Attr. Flags |Attr. Type Code| | Prefix (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +---------------------------+


BGP Operation
BGP-4 Message Exchange
BGP Peers

BGP TCP TCP BGP

Idle Idle
Connect Connect
syn Listen
Syn Sent Syn +Ack Syn Received
Established Ack
Initializing Established
Open Open
Initializing
Open Sent Open Sent

Open Confirm KeepAlive KeepAlive Open Confirm

Established Established
Update Update


BGP Operation
BGP-4 FSM
1 Idle
2
3

6
4 Connect
12
5
11
9
13
Open Sent 10
Active
8 7

14
Open Confirm
15

16
Established


BGP Operation
Current New Event
State State

Idle Idle 1). Error
Connect 2). Start

Connect Idle 3). Any other event
Connect 4). ConnectRetry Timer Expired
Open Sent 5). Transport Protocol Connect Succeeds
Active 6). Transport Protocol Connect Fails

Open sent--- Wait for open from peer
Open Sent Idle 7). Stop, Open Error, Connection Collision,
Hold Timer Expires, or any other event
Open Confirm 8). No Errors
Active 9). Disconnect Notification


BGP Operation
Current New Event
State State
Active Open Sent 10). Transport Connect Protocol Succeeds
Connect 11). ConnectRetry Timer Expired
Active 12). Remote Peer Trying, IP Address Not
Expected
Idle 13). Any Other Event

Open Confirm (waiting notification or keepalive – handshake)
Open Confirm Idle 14). Hold Timer Expired, Notification,
Disconnect, Stop, or any other event

Established 15). Keepalive

Established Idle 16). Notification, UPDATE Message error
Disconnect Notification, Hold Timer
Expired, Stop, or any other event


Summary
 BGP Concept

 BGP Operation

 Route Control

 Configuration




Route Control

Route Selection
 Route with lowest preference value
 Route with highest local preference
 Route with the shortest AS path length
 Route with the lowest origin code ( IGP < EGP < incomplete )
 Route with the lowest MED (cisco-nondeterministic / always-compare-med )
 Routes are local generated
 Routes from EBGP peer
 Routes with the closest next-hop (determined by IGP metric)
 Routes from the peer with lowest router-id
 Routes from the neighbor with lowest IP address


Route Control

Policy Control

Import / Export Policy
Communities
AS path
Route filtering


Route Control

Import / Export Policy
 Per group / neighbor import / export policy
 Used for advertise routes originated from the
local AS
 Used for change / add / delete BGP attributes
 Global specific > Group specific > Neighbor
specific


Route Control
 Applying policies:
bgp {
import global-import-policy-here;
export global-export-policy-here;
group testing-policy {
import group-import-policy-here;
export group-export-policy-here;
neighbor 1.1.1.1 {
import neighbor-import-policy-here;
export neighbor-export-policy-here;
}
}
}


Route Control

 Check the routes received from a peer before
applying an import policy:
show route receive-protocol bgp 1.1.1.1

Check the routes sent to a peer after
applying an export policy:
show route advertising-protocol bgp 1.1.1.1


Route Control

Community
 Well-known community
no-advertise Do not advertise to neighbors
no-export Do not advertise outside your confederation/AS
no-export-subconfed Do not advertise outside your subconfederation

 Define Community
community community-name members [ 100:10 100:30 ];


Route Control

AS Path
 AS Path Regular Expressions
{m,n} at least m and most n repetitions of term.
{m} Exact m repetitions of term
{m,} m or more repetitions of term
* Zero or more repetitions of term
+ One or more repetitions of term
? Zero or one repetitions of term
| One of the two terms on either side of the pipe


Route Control

Route filtering
 Filteringbased on IP prefix / AS path /
Community string / Neighbor / Origin …..
 Import / Export policy


Route Control

Route filtering
 Matching criteria
+ as-path Name of AS path regular expression (BGP only)
+ community BGP community
local-preference Local preference associated with a route
+ neighbor Neighboring router
Origin BGP origin attribute
> prefix-list List of prefix-lists of routes to match
> route-filter List of routes to match


Route Control

Route filtering
 Matching AS Path
policy-statement filtering {
from as-path testing-as-path;
then accept;
}
as-path testing-as-path ".* 200";


Route Control

Route filtering
 Matching Community string
from community testing-community;
then accept;
}
community testing-community members 100:200;


Route Control

Route filtering
 Matching route entry
from route-filter 100.100.0.0/16 orlonger;
then accept;
}


Route Control
Route filtering
 Matching within a group of route entries
prefix-list route-list {
100.100.0.0/16;
100.110.0.0/16;
100.120.0.0/16;
}
from prefix-list route-list;
then accept;
}


Summary
 BGP Concept

 BGP Operation

 Route Control

 Configuration




Configuration
BGP minimum configuration
[routing-options]
autonomous-system <your own AS>;
[protocol bgp]
group BGP-setup {
type [external | internal];
peer-as <peer’s AS>;
neighbor <peer IP address>;
}


Configuration
Example
[protocol bgp]
group BGP-setup {
type external;
peer-as 100;
neighbor 100.1.1.2;
}

[routing-options]
autonomous-system 200;


Configuration
 Set the local-preference
[protocol bgp]
group BGP-setup {
type external;
peer-as 100;
neighbor 100.1.1.2;
}

 Set the MED
[protocol bgp]
group BGP-setup {
type external;
metric-out 200;
peer-as 100;
neighbor 100.1.1.2;
}


Configuration
 Change the origin
[protocol policy-options]
policy-statement change-origin {
from protocol aggregate;
then {
origin incomplete;
accept;
}
}

[protocol bgp]
group BGP-setup {
type external;
export change-origin;
peer-as 100;
neighbor 100.1.1.2;
}


Configuration
 AS-prepend
[policy-options]
policy-statement as-prepend {
then {
as-path-prepend “300 300 300";
accept;
}
}

[protocol bgp]
group BGP-setup {
type external;
export as-prepend;
peer-as 100;
neighbor 100.1.1.2;
}


Configuration
Attach community
[protocol bgp]
group BGP-setup {
type external;
export att-community;
peer-as 100;
neighbor 100.1.1.2;
}

[policy-options]
policy-statement att-community {
then {
community set send-community;
}
}
community send-community members [ 100:10 200:10 ];


Configuration
Route Reflector
[protocol bgp]
group RR-client {
type internal;
cluster 100.1.1.1;
neighbor 100.1.1.2;
neighbor 100.1.1.3;
}
group non-client {
type internal;
neighbor 10.1.1.2;
}
group EBGP {
type external;
peer-as 100;
neighbor 192.168.1.2;
}


Configuration
Confederation
[routing-options]
confederation 200 members [ 65000 65001 ];

[protocol bgp]
group confe {
type external;
peer-as 65001;
neighbor 100.1.1.2;
}


Configuration
 Advertise summary network
[routing-options]
aggregate {
route 202.168.0.0/17 discard;
}
[policy-options]
policy-statement adv-summary {
then accept;
}
[protocol bgp]
group BGP-setup {
type external;
export adv-summary;
peer-as 100;
neighbor 100.1.1.2;
}


Configuration
 Advertise the routing entries in other protocol
[policy-options]
policy-statement adv-ospf {
from protocol ospf;
then accept;
}
[protocol bgp]
group BGP-setup {
type external;
export adv-ospf;
peer-as 100;
neighbor 100.1.1.2;
}


Summary
 BGP concepts

 BGP Operation

 Route Control

 Configuration




Trouble-shooting
 Checking the BGP neighbor status
root@router> show bgp summary
Groups: 1 Peers: 1 Down Peers: 0
Table Tot Paths Act Paths Suppressed History Damp State Pending
inet.0 0 0 0 0 0 0
inet.2 0 0 0 0 0 0
Peer AS InPkt OutPkt OutQ Flaps Last Up/Dwn State|#Active/Received/Damped...
100.1.1.2 65001 275 279 0 0 02:17:30 0/0/0 0/0/0


Trouble-shooting
 Neighbor can’t establish
inet.0 0 0 0 0 0 0
inet.2 0 0 0 0 0 0
Peer AS InPkt OutPkt OutQ Flaps Last Up/Dwn State|#Active/Received/Damped...
100.1.1.2 65001 0 4 0 0 00:00:57 Active

 Enable traceoption
[protocol bgp]
traceoptions {
file bgp-trace;
flag packets detail;
flag open detail;
}


Trouble-shooting
 Monitoring
root@router> monitor start bgp-trace
*** bgp-trace ***
Nov 10 14:53:50
Nov 10 14:53:50 BGP RECV 100.1.1.2+1113 -> 100.1.1.1+179
Nov 10 14:53:50 BGP RECV message type 1 (Open) length 45
Nov 10 14:53:50 BGP RECV version 4 as 65001 holdtime 90 id 192.168.1.2 parmlen 16
Nov 10 14:53:50 MP capability AFI=1, SAFI=1
Nov 10 14:53:50 Refresh capability, code=128
Nov 10 14:53:50 bgp_pp_recv: dropping 100.1.1.2 (External AS 65001), connection collision prefers
100.1.1.2+1113 (proto)
Nov 10 14:53:50 bgp_send: sending 45 bytes to 100.1.1.2 (External AS 65001)
Nov 10 14:53:50
Nov 10 14:53:50 BGP SEND 100.1.1.1+179 -> 100.1.1.2+1113
Nov 10 14:53:50 BGP SEND message type 1 (Open) length 45


Trouble-shooting
 Monitoring
Nov 10 14:53:50 BGP SEND version 4 as 65000 holdtime 90 id 192.168.1.1 parmlen 16
Nov 10 14:53:50 MP capability AFI=1, SAFI=1
Nov 10 14:53:50 bgp_send: sending 19 bytes to 100.1.1.2 (External AS 65001)
Nov 10 14:53:50
Nov 10 14:53:50 BGP SEND 100.1.1.1+179 -> 100.1.1.2+1113
Nov 10 14:53:50 BGP SEND message type 4 (KeepAlive) length 19
Nov 10 14:53:50
Nov 10 14:53:50 BGP RECV 100.1.1.2+1113 -> 100.1.1.1+179
Nov 10 14:53:50 BGP RECV message type 3 (Notification) length 21
Nov 10 14:53:50 BGP RECV Notification code 2 (Open Message Error) subcode 2 (bad peer AS
number)
root@router> monitor stop bgp-trace


Trouble-shooting
 Configuration
Near end
[routing-options]
confederation 200 members [ 65000 65001 65002 ];
[protocol bgp]
group bgp-demo { Far End
type external; [routing-options]
peer-as 65001; autonomous-system 65001;
neighbor 100.1.1.2; confederation 200 members [ 65000 65001 65002 ];
} [protocol bgp]
admin@Jessie# show protocols bgp
group testing {
type external;
peer-as 65002;
neighbor 100.1.1.1;
}


Trouble-shooting
 Logged result:
root@router> file show /var/log/?
Possible completions:
<[Enter]> Execute this command
<filename> Filename to display
/var/log/bgp-trace Size: 2459, Last changed: Nov 7 18:41:08

 Stop logging:
root@router# delete protocols bgp traceoptions
root@router# commit


Trouble-shooting
 Other problem
 Local-address definition (cisco’s update-source)
[protocol bgp]
group <group> {
local-address <local IP address>;
}

 Peer AS mis-configured
 Peer address unreachable
 Mulithop issue for EBGP
[protocol bgp]
group <group> {
multihop;
}


Trouble-shooting
 Problem Report
 “show bgp summary”
 “show bgp neighbor”
 “show bgp group”
 “show version”
 “show configuration”


Summary
 BGP concepts

 BGP Operation

 Route Control

 Configuration




Presentation and command difference between
Juniper and Cisco
Juniper: Cisco:
fxp1 { interface Loopback0
unit 0 { ip address 192.168.1.254 255.255.255.255
family inet { address 172.27.4.172/24; } !
}
interface Ethernet0
}
ip address 172.27.4.173 255.255.255.0
lo0 {
!
unit 0 {
router bgp 200
family inet { address 192.168.1.3/32; } neighbor 192.168.1.3 remote-as 100
} neighbor 192.168.1.3 ebgp-multihop 255
} neighbor 192.168.1.3 update-source Loopback0
routing-options { !
}
group Cisco {
type external;
multihop;
Juniper Cisco
local-address 192.168.1.3;
peer-as 200;
neighbor 192.168.1.254;
}


Juniper and Cisco
root@Juniper> show bgp summary
inet.0 0 0 0 0 0 0
inet.2 0 0 0 0 0 0
Peer AS InPkt OutPkt OutQ Flaps Last Up/Dwn State|
#Active/Received/Damped...
192.168.1.254 200 12 14 0 0 00:05:46 0/0/0 0/0/0

Cisco#show ip bgp summary
BGP table version is 1, main routing table version 1

Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
192.168.1.3 4 100 14 14 1 0 0 00:05:39 0


Juniper and Cisco
root@Juniper> show bgp neighbor

Peer: 192.168.1.254+179 AS 200 Local: 192.168.1.3+3844 AS 100
Type: External State: Established Flags: <>
Last State: OpenConfirm Last Event: RecvKeepAlive
Last Error: None
Options: <Multihop Preference LocalAddress HoldTime PeerAS Refresh>
Local Address: 192.168.1.3 Holdtime: 90 Preference: 170
Number of flaps: 0
Peer ID: 192.168.1.254 Local ID: 192.168.1.3 Active Holdtime: 90
Keepalive Interval: 30
NLRI advertised by peer:
NLRI for this session: inet-unicast
Peer does not support Refresh capability


Juniper and Cisco
Table inet.0 Bit: 10000
Active Prefixes: 0
Received Prefixes: 0
Suppressed due to damping: 0
Table inet.2 Bit: 20000
Active Prefixes: 0
Received Prefixes: 0
Suppressed due to damping: 0
Last traffic (seconds): Received 3 Sent 3 Checked 3
Input messages: Total 16 Updates 0 Refreshes 0 Octets 304
Output messages: Total 18 Updates 0 Refreshes 0 Octets 368
Output Queue[0]: 0
Output Queue[1]: 0
Route Queue Timer: unset Route Queue: empty


Juniper and Cisco
Cisco#show ip bgp neighbors
BGP neighbor is 192.168.1.3, remote AS 100, external link
Index 1, Offset 0, Mask 0x2
BGP version 4, remote router ID 192.168.1.3
BGP state = Established, table version = 1, up for 00:08:45
Last read 00:00:15, hold time is 90, keepalive interval is 30 seconds
Minimum time between advertisement runs is 30 seconds
Received 20 messages, 0 notifications, 0 in queue
Sent 20 messages, 0 notifications, 0 in queue
Connections established 1; dropped 0
Last reset never
No. of prefix received 0
External BGP neighbor may be up to 255 hops away.
Connection state is ESTAB, I/O status: 1, unread input bytes: 0
Local host: 192.168.1.254, Local port: 179
Foreign host: 192.168.1.3, Foreign port: 3844
Enqueued packets for retransmit: 0, input: 0 mis-ordered: 0 (0 bytes)


Juniper and Cisco
Event Timers (current time is 0x2590F0):
Timer Starts Wakeups Next
Retrans 21 0 0x0
TimeWait 0 0 0x0
AckHold 20 17 0x0
SendWnd 0 0 0x0
KeepAlive 0 0 0x0
GiveUp 0 0 0x0
PmtuAger 0 0 0x0
DeadWait 0 0 0x0

iss: 401687383 snduna: 401687774 sndnxt: 401687774 sndwnd: 16384
irs: 486200570 rcvnxt: 486200977 rcvwnd: 15978 delrcvwnd: 406

SRTT: 342 ms, RTTO: 1337 ms, RTV: 326 ms, KRTT: 0 ms
minRTT: 4 ms, maxRTT: 300 ms, ACK hold: 200 ms
Flags: passive open, nagle, gen tcbs

Datagrams (max data segment is 556 bytes):
Rcvd: 25 (out of order: 0), with data: 20, total data bytes: 406
Sent: 38 (retransmit: 0), with data: 20, total data bytes: 390


Juniper and Cisco
Juniper Cisco

no synchronization ( Default behavior ) no synchronization
set policy-options damping cisco bgp damping
set routing-options confederation members bgp confederation
set protocols bgp group Cisco cluster bgp cluster-id

show bgp neighbor show ip bgp neighbor
show bgp summary show ip bgp summary
show route aspath-regex "200" show ip bgp regexp ^200$


Thank you!
http://www.juniper.net

Bgp 1232073634451868-3

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