Cisco Systems 3750E Configuring Fallback Bridging, Fallback Bridging and Switch Stacks, 44-3

Chapter 44 Configuring Fallback Bridging

Configuring Fallback Bridging

Figure 44-1 Fallback Bridging Network Example

Layer 3 switch	Routed port
	172.20.130.1

Host C

172.20.128.1 SVI 1

Host A

VLAN 20

SVI 2 172.20.129.1

Host B

VLAN 30 101240

Fallback Bridging and Switch Stacks

When the stack master fails, a stack member becomes the new stack master by using the election process described in Chapter 5, “Managing Switch Stacks.” The new stack master creates new VLAN-bridge spanning-tree instance, which temporarily puts the spanning-tree ports used for fallback bridging into a nonforwarding state. A momentary traffic disruption occurs until the spanning-tree states transition to the forwarding state. All MAC addresses must be relearned in the bridge group.

Note If a stack master running the IP services feature set fails and if the newly elected stack master is running the IP base feature set, the switch stack loses its fallback bridging capability.

If stacks merge or if a switch is added to the stack, any new VLANs that are part of a bridge group and become active are included in the VLAN-bridge STP.

When a stack member fails, the addresses learned from this member are deleted from the bridge group MAC address table.

For more information about switch stacks, see Chapter 5, “Managing Switch Stacks.”

Configuring Fallback Bridging

These sections contain this configuration information:

•Default Fallback Bridging Configuration, page 44-4

•Fallback Bridging Configuration Guidelines, page 44-4

•Creating a Bridge Group, page 44-4(required)

•Adjusting Spanning-Tree Parameters, page 44-6(optional)

Catalyst 3750-E and 3560-E Switch Software Configuration Guide

OL-9775-02 44-3