ISIS is flapping

[arun.nairrugminiamma1]

I don't see any issues with the Link. However, ISIS appears to be flapping.

sh clns int Gi0/0/0
GigabitEthernet0/0/0 is up, line protocol is up
Checksums enabled, MTU 1497, Encapsulation SAP
ERPDUs enabled, min. interval 10 msec.
CLNS fast switching enabled
CLNS SSE switching disabled
DEC compatibility mode OFF for this interface
Next ESH/ISH in 1 seconds
Routing Protocol: IS-IS (DGN_LTAM)
Circuit Type: level-2
Interface number 0x0, local circuit ID 0x100
Neighbor System-ID: wltdin-ba-munro0-gw
Level-2 Metric: 200, Priority: 64, Circuit ID: wltdin-ba-caba.00
Level-2 IPv6 Metric: 10
Number of active level-2 adjacencies: 1
Next IS-IS Hello in 7 seconds
No hello padding
if state UP

Logs from far end:

LC/0/0/CPU0:Aug 7 16:42:11.292 UTC: bfd_agent[128]: %L2-BFD-6-SESSION_DAMPENING_OFF : Session to neighbor 172.25.168.21 on interface GigabitEthernet0/0/0/19 moved out of Dampened state.
LC/0/0/CPU0:Aug 7 16:42:11.292 UTC: bfd_agent[128]: %L2-BFD-6-SESSION_STATE_UP : BFD session to neighbor 172.25.168.21 on interface GigabitEthernet0/0/0/19 is up
LC/0/0/CPU0:Aug 7 16:42:11.297 UTC: bfd_agent[128]: %L2-BFD-6-SESSION_STATE_DOWN : BFD session to neighbor 172.25.168.21 on interface GigabitEthernet0/0/0/19 has gone down. Reason: Nbor removed session
RP/0/RSP0/CPU0:Aug 7 16:42:14.787 UTC: bgp[1059]: %ROUTING-BGP-5-ADJCHANGE_DETAIL : neighbor 172.25.168.21 Up (VRF: default; AFI/SAFI: 1/1) (AS: 65055)
LC/0/0/CPU0:Aug 7 16:42:14.792 UTC: bfd_agent[128]: %L2-BFD-6-SESSION_DAMPENING_ON : Session to neighbor 172.25.168.21 on interface GigabitEthernet0/0/0/19 entered Dampened state (initial: 2000 ms,secondary: 5000 ms,maximum: 120000 ms).
LC/0/0/CPU0:Aug 7 16:42:26.308 UTC: bfd_agent[128]: %L2-BFD-6-SESSION_DAMPENING_OFF : Session to neighbor 172.25.168.21 on interface GigabitEthernet0/0/0/19 moved out of Dampened state.
LC/0/0/CPU0:Aug 7 16:42:26.308 UTC: bfd_agent[128]: %L2-BFD-6-SESSION_STATE_UP : BFD session to neighbor 172.25.168.21 on interface GigabitEthernet0/0/0/19 is up
RP/0/RSP0/CPU0:wltdin-ba-munro0-gw#

[Georg Pauwen]

Hello,

what platform is this on ?

[arun.nairrugminiamma1]

This is on Mpls

[Giuseppe Larosa · Accepted solution]

Hello @arun.nairrugminiamma1 ,

from the log messages that you have posted it looks like there are issues with BFD rather then with IS-IS itself.

You should try to use less aggressive timers in BFD to see if the problem can be solved in this way.

The platform is clearly an IOS XR device

RP/0/RSP0/CPU0   main CPU

LC/0/0/CPU0   linecard CPU

interface 0/0/0/19   four numbers  means IOS XR and likely an ASR9000

Be also aware of the difference in MTU concepts between IOS/IOS XE and IOS XR (here MTU is a L2 concept)

Hope to help

Giuseppe

[nowy]

What was cousing a issue?