AS9000/XR CDP (LLDP) Issue with Catalyst VLAN Trunk

[HOLGER ALIX]

Hello Community

I have a problem getting CDP (or LLDP) between ASR9000 (IOS-XR 5.3.4/6.1.4) and Catalyst Switches to work.

Case 1: Switch uses default trunk configuration = native VLAN1
CDP (or LLDP) works. Both devices see their neighbours.

Case 2: The connected Catalyst uses a trunk with native VLAN 666 (as an example)
"show cdp neighbour" on the switch shows the ASR9000.
But the ASR9000 does not show the switch!

Case 3: additional subinterface (Layer-3) on the ASR9000 with "encapsulation dot1q 666" suitable for the Catalyst native VLAN666.
Same behavior as Case2.

Configuration example CDP:

--------------------

ASR with L3 interface

Wed Sep 13 06:03:44.859 UTC
interface Gigabit Ethernet 0/0/1/19.666
encapsulation dot1q 666
!

--------------------

switch
Current configuration: 152 bytes
!
interface FastEthernet0/9
switchport trunk encapsulation dot1q
switchport trunk native vlan 666
switchport fashion trunk
tensioning tree portfast
end

Switch#sh cdp neighbors fastEthernet 0/9
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
TEST-CW-88-W3. net. dfs. de
Fas 0/9 162 R ASR9K Ser Gig 0/0/1/19
Switch#

--------------------
But no CDP switch to ASR.....

RP/0/RSP0/CPU0: TEST-CW-88-W3#sh cdp neighbors
Wed Sep 13 06:07:47.860 UTC
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
TEST-CW-88-W4. n Gi0/0/1/0 125 R ASR9K Ser Gi0/0/1/0
TEST-CW-88-W6. n Gi0/0/1/1 162 R I ASR-920-2 Gi0/0/2
TEST-CW-88-W4. n Gi0/0/0/0/0 173 R ASR9K Ser Gi0/0/0/0/0
RP/0/RSP0/CPU0: TEST-CW-88-W3#

--------------------

Same behavior with LLDP (also with "lldp subinterfaces enable")
Do you have any advice?

Thank you very much!
Holger

[xr-escalation · Accepted solution]

hi Holger,

there are several things you could do on the asr9k side to see what's happening with CDP packets:

* check the relevant NP counters (there's a counter for received CDP and two counters for received LLDP packets)
* if these are incrementing, dump the CDP or LLDP packets to confirm the encapsulation that's used by the peer
* https://supportforums.cisco.com/t5/service-providers-documents/asr9000-xr-how-to-capture-dropped-or-lost-packets/ta-p/3140717
* https://supportforums.cisco.com/t5/service-providers-documents/asr9000-xr-troubleshooting-packet-drops-drops-in-np-microcode/ta-p/3155145
* check the LPTS static policer counter to see whether packets are punted to LC CPU: "sh lpts pifib hardware static-police location ..."
* look into CDP or LLDP traces

CDP on sub-interface won't work on XR, but LLDP should work with "lldp subinterfaces enable".

hope this helps,
/Aleksandar