Symptom
- During problem, ASR1k's IPv6 neighbor table is empty because the router is not processing received IPv6 NS messages.
- Due to this, IPv6 to MAC resolution is incomplete, and as such connectivity to Gi0 interface breaks.
- We ran "debug ipv6 icmp" but we were not able to see the NS in debugging.
Conditions
- Tests were conducted on ASR1k:
Issue is triggered when MLD queries are received on Gi0 interface and when there is no other traffic sent to Gi0 interface for 3 minutes or more.
Workaround
- Shut/no shut Gi0 interface.
- on switch before affected device, configuring IPv6 ACL blocking MLD querries (makes sense only in case you are not intentionaly using multicast in management network, but some endpoints generate them anyway)
ipv6 access-list BLOCK-MLD
sequence 10 deny icmp any any mld-query
sequence 20 permit ipv6 any any
Further Problem Description
N/A
