IS-IS and IPv6 LLA next-hop - just Arista, or everyone?

Adam Thompson athompson at
Tue May 4 01:28:33 UTC 2021

Hey, just checking as I don’t have any Cisco or Extreme or Juniper gear running IS-IS to verify myself…

On current Arista (7280SR2K) and older Brocade (MLXe) routers, the IPv6 next-hop address in IS-IS seems to always be the link-local address of the neighbour, instead of any manually-assigned address on the interface. I believe this is *not* the case with Cisco, in particular.  Not sure about other vendors, I don’t have any handy that can run IS-IS.  I don’t appear to have any knobs to control this behaviour, and haven’t found anything related in the docs.

Can anyone confirm that Cisco or other vendors does/do not do this (prefer LLA over GUA)?


Adam Thompson
Consultant, Infrastructure Services
100 - 135 Innovation Drive
Winnipeg, MB, R3T 6A8
(204) 977-6824 or 1-800-430-6404 (MB only)
athompson at<mailto:athompson at><>

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