46-3
Cisco Catalyst Blade Switch 3130 for Dell Software Configuration Guide
OL-13270-01
Chapter46 Configuring Fallback Bri dging Configuring Fallback Bridging
Figure46-1 Fallback Bridging Network Example

Fallback Bridging and Switch Stacks

When the stack master fails, a stack member becomes the ne w s tack m aster b y us ing the election proces s
described in Chapter 5, “Managing Switch S ta ck s.” The new stack master creates new VLAN-bridge
spanning-tree instance, which temporarily puts the spanning-tree ports used for fallba ck 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 bri dge gr oup .
Note If a stack master running the IP services feature set fails and if the n e wly e lec ted st ack mast er is runni ng
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 m em ber a re de lete d f rom t h e bri d ge gr oup
MAC address table.
For more information about switch stacks, see Chapter5, “Managing Switch Stacks.”
Configuring Fallback Bridging
These sections contain this configuration information:
•Default Fallback Bridging Configuration, page 46-3
•Fallback Bridging Configuration Guidelines, page 46-4
•Creating a Bridge Group, page 46-4 (required)
•Adjusting Spanning-Tree Parameters, page 46-6 (optional)

Default Fallback Bridging Configuration

Table46-1 shows the de fault fal lba ck bri dg ing co nfigurati on.
2
01789
Blade
server A
Host C
SVI 1
1
72.20.128.1 172.20.129
.1
Layer 3 switch
Routed port
172.20.130.1
SVI 2
VLAN 20
Blade
server B
VLAN 30