CCNP DC · vPC FAILURE

Nexus: vPC peer-link failure and orphan ports

The vPC domain is up: N1 is primary, N2 secondary, and SW3 forwards on both uplinks. PC3 hangs off N1 and PC2 off N2 on single, non-vPC ports. Break the peer-link and watch what each switch does while the keepalive is still alive.

CCNP Data Center track · Cisco Nexus (NX-OS-style) + Cisco · 4 objectives

Open in simulator More CCNP Data Center labs

Objectives

The simulator ticks each one as soon as the network meets it.

On N1, shut down the peer-link (interface port-channel1, shutdown).
On N2, show vpc: the peer link is down and the secondary has suspended vPC 10 (down*); SW3 now bundles only its N1 uplink.
PC1 still reaches PC3 (192.168.10.30) through the primary, but PC2 (192.168.10.20), an orphan port on the secondary, is unreachable.
Bring the peer-link back (no shutdown) and confirm PC1 reaches PC2 again.

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Before you start

When the peer-link fails but the keepalive still hears the peer, the secondary suspends its vPC member ports to avoid a split network. Anything single-attached to the secondary is then isolated: that is why servers should be dual-attached with vPC, or orphan ports protected with vpc orphan-port suspend.

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.