Gathering Neighbor Information
I can’t stress to you enough how important CDP is. Let’s go through the CDP commands and
please study the output.
The following output shows the show cdp neighbor command used on my ISR router:
Router#sh cdp neighbors
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater
Device ID Local Intrfce Holdtme Capability Platform Port ID
ap Fas 0/1 165 T I AIR-AP124 Fas 0
R2 Ser 0/1/0 140 R S I 2801 Ser 0/2/0
R3 Ser 0/0/1 157 R S I 1841 Ser 0/0/1
R1 Ser 0/2/0 154 R S I 1841 Ser 0/0/1
R1 Ser 0/0/0 154 R S I 1841 Ser 0/0/0
Router#
Another command that will deliver the goods on neighbor information is the show cdp
neighbor detail command (show cdp nei de for short). This command can be run on both
routers and switches, and it displays detailed information about each device connected to the
device on which you’re running the command. Check out this router output for an example:
Router#sh cdp neighbors detail
-------------------------
Device ID: R2
Entry address(es):
IP address: 10.4.4.2
Platform: Cisco 2801, Capabilities: Router Switch IGMP
Interface: Serial0/1/0, Port ID (outgoing port): Serial0/2/0
Holdtime : 135 sec
Version :
Cisco IOS Software, 2801 Software (C2801-ADVENTERPRISEK9-M), Experimental
Version 12.4(20050525:193634) [jezhao-ani 145]
Copyright (c) 1986-2005 by Cisco Systems, Inc.
Compiled Fri 27-May-05 23:53 by jezhao
advertisement version: 2
VTP Management Domain: ''
Corp#
Corp#show cdp entry * protocol
Protocol information for ap :
IP address: 10.1.1.2
Protocol information for R2 :
IP address: 10.4.4.2
Protocol information for R3 :
IP address: 10.5.5.1
Protocol information for R1 :
IP address: 10.3.3.2
Protocol information for R1 :
IP address: 10.2.2.2
Corp#show cdp entry * version
Version information for ap :
Cisco IOS Software, C1240 Software (C1240-K9W7-M), Version 12.3(8)JEA,
RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2006 by Cisco Systems, Inc.
Compiled Wed 23-Aug-06 16:45 by kellythw
Version information for R2 :
Cisco IOS Software, 2801 Software (C2801-ADVENTERPRISEK9-M), Experimental
Version 12.4(20050525:193634) [jezhao-ani 145]
Copyright (c) 1986-2005 by Cisco Systems, Inc.
Compiled Fri 27-May-05 23:53 by jezhao
Version information for R3 :
Cisco IOS Software, 1841 Software (C1841-IPBASE-M), Version 12.4(1c), RELEASE
SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2005 by Cisco Systems, Inc.
Compiled Tue 25-Oct-05 17:10 by evmiller
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