CCIE DC – 1.1.a Link Aggregation – vPC Control Plane

Enjoy this latest post on the control plane functions of the vPC. This is part of the link aggregation section of the exam requirements in CCIE Data Center.

Our previous post on this subject focused on the data plane. You can find it here: 

The vPC Control Plane

The vPC peer link between your vPC peers is the workhorse for the control plane messages (BPDUs, LACP, CFSoE) that must flow between them. The control plane is responsible for the following:

  • Exchange of Layer 2 forwarding tables for the vPC peers – MAC addresses learned on one switch are instantly synced to the other switch using CFSoE; this reduces traffic on the vPC peer link
  • Consistency and compatibility checks – CFSoE exchanges information to ensure both peer support vPC and that he member ports are in a compatible state
  • Sync IGMP snooping information – inbound IGMP traffic triggers synchronization much like MAC address learning
  • Monitor the status of vPC member ports – orphan port behavior may occur due to failure conditions
  • Sync the ARP tables of the vPC peers – again CFSoE is used to keep these important tables in sync; this speeds convergence if one of the vPC peers must reload
  • Determine the primary and secondary vPC peer devices – the primary is responsible for the processing of BPDUs; the election is non-preemptive
  • Agree on LACP and STP parameters – this is needed because the vPC announces itself to the downstream switch as a single logical switch

For even more information – check out this Cisco documentation at
Pearson Education (InformIT)

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