CDP Issue(

Unanswered Question
May 14th, 2008
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Dear ALL

If i am using CDP on my Routers iam not able to discover any CDP neighbours and

if i am using CDP on switches i am able to discover all LAN Devices

Could some body help me

Out put of CDP on my ROUTERS is below,

#sh cdp

Global CDP information:

Sending CDP packets every 60 seconds

Sending a holdtime value of 180 seconds

Sending CDPv2 advertisements is enabled


sh cdp traffic

CDP counters :

Total packets output: 789061, Input: 0

Hdr syntax: 0, Chksum error: 0, Encaps failed: 0

No memory: 0, Invalid packet: 0, Fragmented: 0

CDP version 1 advertisements output: 0, Input: 0

CDP version 2 advertisements output: 789061, Input: 0


sh cdp

Global CDP information:

Sending CDP packets every 60 seconds

Sending a holdtime value of 180 seconds

Sending CDPv2 advertisements is enabled


sh cdp interface

Ethernet0/0 is up, line protocol is up

Encapsulation ARPA

Sending CDP packets every 60 seconds

Holdtime is 180 seconds


######sh cdp ne

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


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mahmoodmkl Wed, 05/14/2008 - 00:39
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Can u verify it the other end is enabled for CDP.



UCBNOCWAN Wed, 05/14/2008 - 00:57
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Other end it is enabled

from all the switches i am able to see the neghbours excpet the router.

mvandorp Wed, 05/14/2008 - 01:19
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What is your interface configuration? Is an ACL blocking things?


UCBNOCWAN Wed, 05/14/2008 - 18:13
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There is ACL on ethernet interface (LAN)

Extended IP access list 141

10 deny tcp any any eq 1639 (30717 matches)

20 permit ip any any (1326742325 matches)

My ethernet config is below

interface Ethernet0/0

description ### LAN ###

ip address ##########

ip access-group 141 in

ip route-cache flow


standby ip ##########

standby preempt

how to configure IP CDP

Please advice on the same.

Edison Ortiz Wed, 05/14/2008 - 20:12
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CDP is enabled by default and no need to configure it. Your original post confirms CDP is running on that interface.

Can you post the portion of the config from the switchport connected to this router?

You may be experiencing a duplex mismatch issue which is affecting CDP. I noticed your Ethernet interface is running half-duplex, you must match this duplex setting on the switchport as well.



sanjay.khurana Wed, 05/14/2008 - 06:24
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U need to configure IP cdp on interface also.

and after that u can check the cdp status..

bmcginn Wed, 05/14/2008 - 20:09
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use "cdp run" in global configuration on both devices, or if you don't want CDP on a particular interface, you can disable it on the interface using "no cdp enable"

cyptic Fri, 05/16/2008 - 04:28
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We need so see your complete interface configuration both for the router and for the switch. Have you configured any router interface as a dot1q-trunk? Have you changed the native vlan in some of the units?


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