Configuring Metro Features
December 2005 © Foundry Networks, Inc. 8 - 19
Figure 8.7 VSRP mesh – redundant paths for Layer 2 and Layer 3 traffic
In this example, two Foundry devices are configured as redundant paths for VRID 1. On each of the devices, a
Virtual Router ID (VRID) is configured on a port-based VLAN. Since VSRP is primarily a Layer 2 redundancy
protocol, the VRID applies to the entire VLAN. However, you can selectively remove individual ports from the
VRID if needed.
Following Master election (described below), one of the Foundry devices becomes the Master for the VRID and
sets the state of all the VLAN’s ports to Forwarding. The other device is a Backup and sets all the ports in its VRID
VLAN to Blocking.
If a failover occurs, the Backup becomes the new Master and changes all its VRID ports to the Forwarding state.
Other Foundry devices can use the redundant paths provided by the VSRP devices. In this example, three
Foundry devices use the redundant paths. A Foundry device that is not itself configured for VSRP but is
connected to a Foundry device that is configured for VSRP, is VSRP aware. In this example, the three Foundry
devices connected to the VSRP devices are VSRP aware. A Foundry device that is VSRP aware can failover its
link to the new Master in sub-second time, by changing the MAC address associated with the redundant path.
When you configure VSRP, make sure each of the non-VSRP Foundry devices connected to the VSRP devices
has a separate link to each of the VSRP devices.
Layer 2 and Layer 3 Redundancy
You can configure VSRP to provide redundancy for Layer 2 only or also for Layer 3.
• Layer 2 only – The Layer 2 links are backup up but specific IP addresses are not backed up.
• Layer 2 and Layer 3 – The Layer 2 links are backup up and a specific IP address is also backed up. Layer 3
VSRP is the same as VRRPE. However, using VSRP provides redundancy at both layers at the same time.
Layer 2 Switches support Layer 2 VSRP only. Layer 3 Switches support Layer 2 and Layer 3 redundancy. You
can configure a Layer 3 Switch for either Layer 2 only or Layer 2 and Layer 3. To configure for Layer 3, specify the
IP address you are backing up.
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