Replacing some old cisco routers with 8500's running 17.9.4a. They are connected to a Nexus 7K, on the same card. The routers can ping one another and establish BGP but they will not establish the HSRP adjacently across the 7K. If the 8500's are connected directly, HSRP will establish. The 7K config is very simple, just both ports in the same VLAN for each router uplink.
I think IGMP snooping is enabled by default on the Nexus, which might prevent the multicast packets used by HSRP (224.0.0.2) from being propagated. Try and disable IGMP snooping at least for the Vlan the HSRP ports belong to...
IGMP snooping should not block / process link local multicast addresses but the Nexus may be directing the HSRP hellos to its main cpu instead of propagating them for some VPC feature.
Thanks for the responses and insight. We performed some addition testing today. We moved these connections down to a Nexus 5K and HSRP works across them. Same VLANs that were tested on the 7K's. The 5K's are connected to the 7Ks via VPC. We do suspect it could be related to a local VPC issue between the 7Ks. When you look at a trace, you can see the traffic going to the correct MAC addresses and the fact that you have L2 connectivity and can ping across the routers even when HSRP does not work seems odd.
