VRRP or VRRP-E over an MCT-Enabled Network

To interface a Layer 2 MCT deployment with a Layer 3 network and add redundancy at the Layer 3 level, MCT can be configured with the Virtual Router Redundancy Protocol (VRRP). The standard VRRP mode is master-backup, and all traffic is forwarded through the master. In VRRP-E server virtualization, multiple VRRP standby devices are supported, and each device can be configured to route to an upstream Layer 3 network. This provides efficient deployment for both Layer 2 and Layer 3 networks.

The MCT device acting as a backup router will forward all packets destined to VRRP or VRRP-E virtual MAC address to the VRRP or VRRP-E master router for routing. The VRRP or VRRP-E backup learns the virtual MAC address while processing the VRRP hello message from the VRRP master. Both data traffic and VRRP or VRRP-E control traffic travel through the ICL unless the short-path forwarding feature is enabled (VRRP-E only).

VRRP or VRRP-E and VRRP-E2 short-path forwarding (SPF) should be enabled, if required. If VRRP is deployed or VRRP-E is deployed without the short-path forwarding feature on the VRRP-E backup, it is likely that almost 50 percent of CCEP to CEP traffic (and as much as 100 percent of traffic in the worst case) can pass through the ICL from the backup to the master device. This fact should be considered when designing ICL capacity in the network.

When one MCT device acts as a VRRP or VRRP-E master and the peer device is the VRRP or VRRP-E backup, the following behavior is observed:

  • Frames sent to the VRRP or VRRP-E virtual MAC address are forwarded to the VRRP or VRRP-E master device for routing. The VRRP-E MAC address is learned by the other MCT device that acts as a backup router.
  • Both data traffic and VRRP-E control traffic received by the VRRP backup from an MCT client must travel through the ICL, unless the short-path forwarding feature is enabled.

When both MCT devices act as the VRRP or VRRP-E backup, the following traffic behavior is observed:

  • Frames sent to the VRRP or VRRP-E virtual MAC address are forwarded to the VRRP or VRRP-E master router for routing.
  • The VRRP-E MAC address is learned by both MCT devices acting as backup routers.
  • Both data traffic and VRRP-E control traffic travel through the links connecting them to the VRRP or VRRP-E master.
Parent topic: Layer 3 Behavior with MCT