[j-nsp] MC-LAG on QFX5100

[William McLendon]

if you are running a routing protocol over the particular VLAN on the MC-LAG peers (which is a supported config in Junos MC-LAG implementation) make sure you are running VRRP between the MC-LAG peers, even though it seems unnecessary.  VRRP seems required for any ARP sync to occur for a given IRB interface.  Without it one side can learn the ARP entry but not the other.  Clearing arp cache seems to fix it temporarily but then it pops up again after ARP ages out.

We ran into this issue in a similar scenario with MC-LAG L2-only switches where you could only ping the default gateway from one node unless you issued a clear arp, and then it would work until ARP timer ran out again.  Once we configured VRRP that issue was resolved.


Thanks,

Will