Cisco CDP protocol tutorial, configuration with examples. Cisco discovery Protocol on live network.

1. CDP (Cisco Discovery Protocol). Document Version 1.0
Deepak Kumar (deepuverma@outlook.com), Call: - +91 - 8875332931 / 9214012330
Updated material may be found at http://www.deepuverma.in
LinkedIn: - https://in.linkedin.com/in/engdeepak Twitter: - https://twitter.com/Deepakkhw
Cisco Discovery Protocol (CDP) is a Cisco propriety protocol
used to collect information about locally attached Cisco switches and routers. CDP is enabled by default
on all IOS enabled routers and switches. CDP sends out updates every 60 seconds and hold time is 180
seconds. CDP is a proprietary Data Link Layer protocol. A device periodically sends out a CDP
advertisement every 60 seconds using the layer 2 multicast address 01:00:0c:cc:cc:cc which is also used
by VTP. It is available in IOS from version 10.3. Routers and catalyst switches support CDP. CDP Version-
2 (CDPv2) is the most recent release of the protocol and provides more intelligent device tracking
features.
CDP will provide the following information about directly connected neighbors:
• Device ID – hostname of remote router/switch
• Local Interface – interface that remote router/switch is directly connected to
• Holdtime – amount of time before remote device information is purged from CDP table
• Capability – Type of remote device (router, switch, host)
• Platform – Model of remote device.
Limitations
CDP is cisco proprietary Protocol so it is not working on multivendor network. It is also not available on
below of ISO version 10.3 routers and switches.
Alternative of CDP is LLDP Protocol (Will Discuss next time).
CDP Testing
As per image, take a network Diagram for testing CDP Protocol.

2. CDP (Cisco Discovery Protocol). Document Version 1.0
Deepak Kumar (deepuverma@outlook.com), Call: - +91 - 8875332931 / 9214012330
Updated material may be found at http://www.deepuverma.in
LinkedIn: - https://in.linkedin.com/in/engdeepak Twitter: - https://twitter.com/Deepakkhw
Getting Neighbor Information on R0:-
Because the router stores the CDP information in its cache memory, you can view it with a show
command. It will only show information about directly connected devices since CDP packet aren't
passed through the device.
R0#sho cdp neighbors
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone
Device ID Local Intrfce Holdtme Capability Platform Port ID
Switch Fas 0/0 124 S 2950 Fas 0/1
R1 Ser 0/0/1 133 R C1841 Ser 0/0/1
R1 Ser 0/0/0 133 R C1841 Ser 0/0/0
R0#
R0#
Let’s Check CDP Entry on R0:-
The sho cdp entry [device id] command shows more information about the specified neighbor.
R0#sho cdp entry R1

3. CDP (Cisco Discovery Protocol). Document Version 1.0
Deepak Kumar (deepuverma@outlook.com), Call: - +91 - 8875332931 / 9214012330
Updated material may be found at http://www.deepuverma.in
LinkedIn: - https://in.linkedin.com/in/engdeepak Twitter: - https://twitter.com/Deepakkhw
Device ID: R1
Entry address(es):
IP address : 192.168.3.5
Platform: cisco C1841, Capabilities: Router
Interface: Serial0/0/1, Port ID (outgoing port): Serial0/0/1
Holdtime: 133
Version :
Cisco IOS Software, 1841 Software (C1841-ADVIPSERVICESK9-M), Version 12.4(15)T1,
RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2007 by Cisco Systems, Inc.
Compiled Wed 18-Jul-07 04:52 by pt_team
advertisement version: 2
Duplex: full
---------------------------
Device ID: R1
Entry address(es):
IP address : 192.168.2.2
Platform: cisco C1841, Capabilities: Router
Interface: Serial0/0/0, Port ID (outgoing port): Serial0/0/0
Holdtime: 133
Version :
Cisco IOS Software, 1841 Software (C1841-ADVIPSERVICESK9-M), Version 12.4(15)T1,
RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2007 by Cisco Systems, Inc.
Compiled Wed 18-Jul-07 04:52 by pt_team
advertisement version: 2
Duplex: full
---------------------------
R0#

4. CDP (Cisco Discovery Protocol). Document Version 1.0
Deepak Kumar (deepuverma@outlook.com), Call: - +91 - 8875332931 / 9214012330
Updated material may be found at http://www.deepuverma.in
LinkedIn: - https://in.linkedin.com/in/engdeepak Twitter: - https://twitter.com/Deepakkhw
To display port and interface information:
Router# sh cdp interface
To disable CDP on an interface:
Router(config-if)# no cdp enable
To globally disable CDP:
Router(config)# no cdp run
-----------------------------End CDP Document Version 1.0 by Deepak Kumar -----------------------------------
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