Objectives
The simulator ticks each one as soon as the network meets it.
From PC1, ping PC4 (192.168.20.40): it fails, and the reason names vPC loop avoidance.
Enable peer-gateway in vpc domain 10 on both peers.
show vpc on N1: Peer Gateway Enabled.
Ping PC4 (192.168.20.40) from PC1 again: it works.
Before you start
A frame for N2’s own router MAC can arrive on N1 (SW3 hashes it there) and cross the peer-link. vPC loop avoidance stops a packet that crossed the peer-link from leaving on a vPC, so N2 drops it after routing. peer-gateway lets each peer route frames sent to the other peer’s router MAC itself. NX-OS reminds you to disable IP redirects on the SVIs.
Concept
vPC pairing rules: keepalive VRF, type-1 checks, peer-switch, peer-gateway
Two Nexus switches become vPC peers only when they agree: the same domain ID, a trunk peer-link that is up, and a peer-keepalive they have both heard. The keepalive runs in VRF management (mgmt0) unless told otherwise. Once paired, global and per-vPC type-1 parameters must match, or vPCs are suspended. peer-switch and peer-gateway make the pair behave as one switch for spanning tree and for routing.
Concept
vPC: one port-channel across two Nexus switches
A virtual port-channel lets a downstream switch or server bundle links that end on two different Nexus switches. The two switches form a vPC domain: they synchronise over a peer-link and check each other is alive over a separate peer-keepalive. Toward the access switch they act as one LACP partner, so both uplinks forward and spanning tree blocks nothing.
