VRRP/VRRP-E and VRRP-E2 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 fty percent of CCEP to CEP trac (and as much as a hundred percent
of trac 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/VRRP-E master and the peer device is the VRRP/VRRP-E backup, the following behavior is
observed:
• Frames sent to the VRRP/VRRP-E virtual MAC address are Layer 2-switched to the VRRP/VRRP-E master device for routing.
The VRRP-E MAC address is learned by the other MCT device that acts as backup router.
• Both data trac and VRRP-E control trac 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 trac behavior is observed:
• Frames sent to the VRRP/VRRP-E virtual MAC address are Layer 2 forwarded to the VRRP/VRRP-E master router for routing.
• The VRRP-E MAC address is learned by both MCT devices acting as backup routers.
• Both data trac and VRRP-E control trac travel through the links connecting them to the VRRP/VRRP-E master.
VRRP-E short-path forwarding and revertible option
At the VRRP-E VRID
conguration level, use the following command to enable short-path forwarding.
device(config-if-e1000-vrid-2)# short-path-forwarding revert-priority 60
Syntax: [no] short-path-forwarding [ revert-priority value]
The revert-priority value in the short-path-forwarding command works in conjunction with the track-port command to control
forwarding behavior.
The track-port command monitors the status of the outgoing port on the backup. Command behavior can cause short-path forwarding
to be disabled temporarily. This happens because as one or more ports tracked by the track-port command go down, the current priority
of the VRRP-E is lowered by a
specic amount congured in the track-port command for each port. Once the current-priority of the
VRRP-E is lower than the threshold value congured as the revert-priority value, short-path forwarding is temporarily suspended
because the VRRP-E reverts back to its default forwarding behavior.
To counter this behavior, use the revert-priority value in the short-path-forwarding command as a control threshold. Short-path
forwarding resumes as soon as the VRRP-E priority becomes higher than the revert priority threshold. The VRRP-E priority increases by
the value congured for the track port command as each of the ports tracked by the command becomes active again.
OSPF and BGP over an MCT-enabled network
OSPF and BGP adjacencies can be established over the MCT member VLANs between any combinations of network elements in the
MCT topology.
The combinations that can be established are:
• Devices connected to MCT cluster over CEP ports
• Devices connected to MCT cluster over non-MCT ports
• MCT cluster devices
• MCT clients
• Devices behind MCT clients
Layer 3 behavior with MCT
FastIron Ethernet Switch Layer 3 Routing
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