CDP acts weird

[OLE DREWS JENSEN]

I have 3 Cisco Catalyst 2960S switches on a mesh network: A (host), B and C.

If I do a sh cdp nei on switch A, I can see B and C.

If I do a sh cdp nei on switch B, I can only see C, and on C I can only see B.

I can ping all from all.

What could be the reason for this?

Thanks,

Ole

[Flavio Miranda]

Hi

 Weird indeed.

 But, if you have CDP per interface this could be because interfaces on A have no CDP enable while on B and C have.

 This way they can see each other and A can see both of them but they can not see A

[OLE DREWS JENSEN]

Thanks for your prompt reply.

They use the same ports connecting to the mesh. The A switch is connected to the mesh on port 48, and B and C both are connected on their port 24.

[Flavio Miranda]

Ok, but they have CDP enable on the interface or global ?

 It seems to be C and B is propagating CDP, while A is only reading  propagated CDP but not propagating it.

[MHM Cisco World]

I Think because of mesh the SW send only one cdp whcih receive from only one SW 

Do debug cdp { packets | adjacency | events } )

Check if cdp packet receive from SW with issue 

[OLE DREWS JENSEN]

Thank you both. I've enabled CDP on both the Interface and globally, and even set the v2 advertisements.

The debug doesn't show any errors.

[MHM Cisco World]

Do you see packet from missing SW?

Mesh can causes the cdp exchange between two SW. 

[OLE DREWS JENSEN]

Not sure I'm using the debug correctly. I'm a bit rusty in my Cisco commands.

Neither switch B nor switch C can see switch A using the SH CDP NEI command. What should I run and on which switch?

Thanks.

[OLE DREWS JENSEN]

To provide more info: I have a 4th switch (2960) we can call D connected to switch A on a different mesh. Both can see each other in CDP.

[OLE DREWS JENSEN]

[Flavio Miranda]

It is possible to see the show run-config from Switch A ?

[OLE DREWS JENSEN]

Cropped RUNNING-CONFIG:

GE-Switch-1#show running-config
Building configuration...

Current configuration : 5531 bytes
!
! Last configuration change at 07:30:25 UTC Sat Feb 25 2012
! NVRAM config last updated at 07:27:54 UTC Sat Feb 25 2012
!
version 15.0
no service pad
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname GE-Switch-1
!
boot-start-marker
boot-end-marker
!
enable secret 5 $1$Ndtx$JcbipWplePKmb9DtG47Yw0
!
no aaa new-model
clock timezone UTC -6 0
clock summer-time UTC recurring
switch 1 provision ws-c2960s-48ts-l
!
!
ip device tracking
!
!
crypto pki trustpoint HTTPS_SS_CERT_KEYPAIR
enrollment selfsigned
serial-number
revocation-check none
rsakeypair HTTPS_SS_CERT_KEYPAIR
!
!
crypto pki certificate chain HTTPS_SS_CERT_KEYPAIR
certificate self-signed 01
3082026C 308201D5 A0030201 02020101 300D0609 2A864886 F70D0101 04050030
45311530 13060355 0403130C 47452D53 77697463 682D312E 312C300F 06035504
05130841 39443145 46383030 1906092A 864886F7 0D010902 160C4745 2D537769
7463682D 312E301E 170D3133 30383239 31373033 33305A17 0D323030 31303130
30303030 305A3045 31153013 06035504 03130C47 452D5377 69746368 2D312E31
2C300F06 03550405 13084139 44314546 38303019 06092A86 4886F70D 01090216
0C47452D 53776974 63682D31 2E30819F 300D0609 2A864886 F70D0101 01050003
818D0030 81890281 8100C5E7 C4DC1F07 D17A9EBC 165DA9B1 DC934F7F 18A55208
0FE1D054 04020346 41B2FDEA 803B5ABA EB71C0A0 4D6E5E94 A40E4D86 75D55DB3
2BD0BACC C8559205 5FAEE105 6606B152 C01B7E88 A3C07975 F03E8577 6285EACC
E6DD2A4F 11DE09BC 614C5D6F 2E307EA8 E6A1C596 85F2891C 60359D9B A36237FF
92B2F13D 7B4A0ACF 1A770203 010001A3 6C306A30 0F060355 1D130101 FF040530
030101FF 30170603 551D1104 10300E82 0C47452D 53776974 63682D31 2E301F06
03551D23 04183016 8014E7B3 5B41C5F6 47807830 80EB88EC 447FB72B 8593301D
0603551D 0E041604 14E7B35B 41C5F647 80783080 EB88EC44 7FB72B85 93300D06
092A8648 86F70D01 01040500 03818100 1F86FA26 1429B0F1 C8089B27 C5B213BC
C519F2ED 9C883562 689DDCEF A3A90019 62C5E725 FD3DD1EF 20444729 0B8DE124
76786178 FCDFDFBC E979A470 F507B78F D7F1DB7E 5BAB49E9 5A0E3DCB 9DC99184
88962B89 587FBD00 4C2050A3 EA416587 B7C69154 A16BD7FA C2773A71 EFBB8FD9
4C28567C 5E41F32F 69312AF4 89F05E0E
quit
spanning-tree mode pvst
spanning-tree extend system-id
!
vlan internal allocation policy ascending
!
interface GigabitEthernet1/0/19
description "LUMEN NLAN to SWC/NW/SE/DFW"
!
interface GigabitEthernet1/0/47
description SWITCH 3548
speed 1000
duplex full
!
interface GigabitEthernet1/0/48
description COGENT TO BRANCHES
speed 1000
duplex full
!
interface Vlan1
ip address 10.29.60.1 255.0.0.0
!
ip default-gateway 10.0.0.44
ip http server
ip http secure-server
!
cdp timer 15
!
line con 0
line vty 0 4
exec-timeout 0 0
password xxxxxxxxxx
login
line vty 5 15
exec-timeout 0 0
password xxxxxxxxxx
login
!
end

GE-Switch-1#

[MHM Cisco World]

The only reason left is that this not cisco SW and it use lldp not cdp. 

Can you confirm? 

[OLE DREWS JENSEN]

All switches are Cisco switches. A, B and C are Cisco Catalyst 2960S and D is 2960.

A and B have 48 "regular" ports and C and D have 24 "regular" ports.

[MHM Cisco World]

this simple use debug cdp packet check if SW A receive any CDP frame from B and C.
the interface appear in debug cdp packet