Symptom
IS-IS may not update a route via ECMP paths to same neighbor after reconfiguring metric value on one of the ECMP links.
Conditions
This issue is PI and will affect only these releases: 7.4.2 7.5.2
IS-IS configuration with:
- point-to-point links
- link-id not advertised in its own LSP database (IS-Extend subtlvs)
Note that with segment-routing or mpls traffic-eng config enabled under IS-IS, the link-id will automatically be advertised.
router isis
address-family ipv4 unicast
mpls traffic-eng
router isis
address-family [ipv4 | ipv6] unicast
segment-routing
Problem will not happen when any of the above is configured.
Workaround
One of:
- wait for next periodic FSPF run (max delay: 15 mins)
- if acceptable, configure ‘advertise link attributes’ to force ISIS to advertise link-id:
router isis
address-family [ipv4 | ipv6] unicast
advertise link attributes
Further Problem Description
Periodic FSPF every 15 min or any subsequent FSPF run (due to config/topology change) will correct the problem.
