Currently experiencing a very weird problem (Which I shall raise a TAC for at some point) but was wondering if anyone could help before I do?
We recently upgraded four Nexus 5548UP switches from 6.0.2 N2 to 7.0.1.N1(1a) they are two pairs both in vPC's but connected via fabricpath in a kind of mesh.
HSRP was configured on each switch with priority given to switch 1 then 2 and then 3 and then 4. This worked perfectly until we upgraded to the above version and now when switch 1 is up packets are dropped in every which way as if there is vPC/HSRP issue. If we shutdown switch 1 and allow switch 2 to take over HSRP all is ok. Equally if I shutdown the SVI on switch 1 and 2 and let 3 and four take over HSRP duties all is equally well.
Another thing I've noticed is that all switches are set to preempt, so in the event of a failure the topology will hopefully reset with switch 1 being the primary, 2 being the backup etc etc. Even though switch 1 is set with a higher priority than the other three when it is turned back on it will not take the active role (You can see in the coup info being sent but its like the other switches are ignorning it).
I'll post some config tomorrow but annoyingly this hasnt changed for over 2 years and is now no longer working.
Sorry for the huge delay in replying but I forgot this was open in the forum. Just for others information this was down to a fatal bug with HSRP in this build. It caused multiple issues which was fixed with an upgrade to a later version as confirmed by TAC. We seem to be one of a handful of people who experienced this issue. I'd recommend anyone experiencing this upgrading to a later version and confirming with Cisco TAC where choice to confirm the bug is no longer present.