04-30-2007 03:48 PM - edited 03-05-2019 03:46 PM
I am attempting to update our network diagrams and am finding with some sites that the neighbours do not show up.
CDP is enabled on the switch and router from what I can tell.
The router is a 3550 and switch is a 2950, for this particular site the core router will not show any neighbours, although if you connect to a switch it will show the router.
As with some switches will show their neighbours and others will not.
Any pointers in what to check, or even with this occuring is there an easy way to find out neighbours of a device without CDP working.
Thanks
Dan
04-30-2007 05:49 PM
Dan,
Have you tried comparing the configs between what's working from what's not working? Can you post the config?
hieu
04-30-2007 06:11 PM
Here is the config of the router..
!
! Last configuration change at 09:14:41 Eastern Mon Apr 30 2007
!
version 12.1
no service pad
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname ---
!
enable secret xxx
!
clock timezone Easternstandard 10
clock summer-time Easternsummer recurring last Sun Oct 2:00 last Sun Mar 3:00
ip subnet-zero
ip routing
!
mls qos
!
spanning-tree extend system-id
!
!
!
interface Loopback0
description Management_Interface
ip address xxx.xxx.xxx.xxx 255.255.255.255
!
interface Port-channel1
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 10,20,100,300,1002-1005
switchport mode trunk
no ip address
!
interface GigabitEthernet0/1
description WAN_Interface
no switchport
ip address xxx.xxx.xxx.xxx 255.255.255.252
!
interface GigabitEthernet0/2
description Spare_trunk_Tie
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 10,20,100,300,1002-1005
switchport mode trunk
no ip address
!
interface GigabitEthernet0/3
description Spare_trunk_Tie
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 10,20,100,300,1002-1005
switchport mode trunk
no ip address
!
interface GigabitEthernet0/4
description Spare_trunk_Tie
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 10,20,100,300,1002-1005
switchport mode trunk
no ip address
!
interface GigabitEthernet0/5
description Spare_trunk_Tie
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 10,20,100,300,1002-1005
switchport mode trunk
no ip address
!
interface GigabitEthernet0/6
description Spare_trunk_Tie
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 10,20,100,300,1002-1005
switchport mode trunk
no ip address
!
interface GigabitEthernet0/7
description Spare_trunk_Tie
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 10,20,100,300,1002-1005
switchport mode trunk
no ip address
!
interface GigabitEthernet0/8
description Spare_trunk_Tie
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 10,20,100,300,1002-1005
switchport mode trunk
no ip address
!
interface GigabitEthernet0/9
description Spare_trunk_Tie
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 10,20,100,300,1002-1005
switchport mode trunk
no ip address
!
interface GigabitEthernet0/10
description Spare_trunk_Tie
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 10,20,100,300,1002-1005
switchport mode trunk
no ip address
!
interface GigabitEthernet0/11
description Spare_trunk_Tie
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 10,20,100,300,1002-1005
switchport mode trunk
no ip address
duplex full
speed 1000
channel-group 1 mode on
!
interface GigabitEthernet0/12
description Server_Switch
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 10,20,100,300,1002-1005
switchport mode trunk
no ip address
duplex full
speed 1000
channel-group 1 mode on
!
interface Vlan1
description Not in Use
no ip address
shutdown
!
interface Vlan10
description IT_Faculty
no ip address
ip access-group ITfaculty in
!
interface Vlan20
description ITFaculty
ip address xxx.xxx.xxx.xxx 255.255.254.0
ip access-group ITfaculty in
!
interface Vlan100
description Data
ip address xxx.xxx.xxx.xxx 255.255.254.0
!
interface Vlan300
description Voice
ip address xxx.xxx.xxx.xxx 255.255.254.0
ip helper-address xxx.xxx.xxx.xxx
!
ip classless
ip route 0.0.0.0 0.0.0.0 xxx.xxx.xxx.xxx name LastResort
ip http server
!
04-30-2007 07:27 PM
Daniel
I believe that there is a significant clue about what is going on in this statement from your post: "The router is a 3550 and switch is a 2950, for this particular site the core router will not show any neighbours, although if you connect to a switch it will show the router." I believe that it confirms what the config shows which is that CDP is running on the router.
My guess is that CDP is not running on the switch interfaces. It would be helpful if you would post the output of show cdp interface from both the router and the switch.
HTH
Rick
04-30-2007 07:40 PM
*** Example From Switch ***
6073--MG12ES001#show cdp
Global CDP information:
Sending CDP packets every 60 seconds
Sending a holdtime value of 180 seconds
Sending CDPv2 advertisements is enabled
6073--MG12ES001#
6073--MG12ES001#show cdp interface
FastEthernet0/1 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 60 seconds
Holdtime is 180 seconds
FastEthernet0/2 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 60 seconds
Holdtime is 180 seconds
FastEthernet0/3 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 60 seconds
Holdtime is 180 seconds
*** Example from router ***
6073--AG23LR002#show cdp
Global CDP information:
Sending CDP packets every 60 seconds
Sending a holdtime value of 180 seconds
Sending CDPv2 advertisements is enabled
6073--AG23LR002#show cdp inter
6073--AG23LR002#show cdp interface
GigabitEthernet0/1 is up, line protocol is up
Encapsulation ARPA
Sending CDP packets every 60 seconds
Holdtime is 180 seconds
GigabitEthernet0/2 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 60 seconds
Holdtime is 180 seconds
GigabitEthernet0/3 is down, line protocol is down
Encapsulation ARPA
Sending CDP packets every 60 seconds
Holdtime is 180 seconds
Thanks
04-30-2007 08:22 PM
Daniel
Thanks for posting the additional information. While it does not give me the answer, perhaps it allows us to get a bit deeper into the issue. It does show that CDP is globally enabled on the router and on the switch.
I note that the output indicates that the router gig0/1 is an access port and is up/up but that gig0/2 and gig0/3 are trunk ports and are down/down. Is there some issue with these ports? Perhaps we need some output to be posted to show who sees neighbors on what interfaces.
HTH
Rick
05-01-2007 02:43 PM
Hi Rick,
From the information I have been able to gather, it appears there are no devices on these ports mentioned above, there are devices connected only to those ports showing as up/up.
Hope I am on the right track here :)
Dan
05-01-2007 07:01 PM
Dan
If there are no devices connected on these ports it would certainly explain why they are down/down.
Rick
05-02-2007 07:01 PM
Hi Dan,
I think you should specify which port on the switch and the router were being used to connect to each other in order to avoid the confusion of up/up or down/down.
Jeff
05-05-2007 09:11 AM
I have seen this at times with cisco and it does behave as you have suggested . A few times I have been able to fix it by doing a "clear interface " on the attaching interfaces and cdp would start showing up again otherwise you may be stuck either living with it or reload the devices to see if that would fix it . Might want to consider upgrading the 3550 it looks like it is still running 12.1 code which is way out of date for the 3550 .
05-07-2007 04:46 PM
Thanks all for you reponses and time, we have updated the names on each switch to bring them into standard and they are now showing up on CDP.
Got love these problems.
Dan
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