[c-nsp] vPC peer-link decrease the TTL (Y Ham)

[Andrew Clark]

You didn't mention platform and code. Dynamic routing protocol adjacency over vPC is a newer feature (7.2+ for N7K)  See below for supported topologies:

http://www.cisco.com/c/en/us/td/docs/switches/datacenter/sw/nx-os/interfaces/configuration/guide/b-Cisco-Nexus-7000-Series-NX-OS-Interfaces-Configuration-Guide-Book/configuring-vpcs.html#concept_F862A25175DE4C738065F0EDA6F5D8C0

If your use case is not supported or you are using older code, you should consider normal L3 links instead.