Cisco Systems 3560 Manual Do Utilizador

This chapter describes how to configure fallback bridging (VLAN bridging) on the Catalyst 3560 switch. 
With fallback bridging, you can forward non-IP packets that the switch does not route between VLAN 
bridge domains and routed ports.

To use this feature, the switch must be running the IP services image (formerly known as the enhanced 
multilayer image [EMI]). For complete syntax and usage information for the commands used in this 
chapter, see the Cisco IOS Bridging and IBM Networking Command Reference, Volume 1 of 2, Release 
12.2 from the Cisco.com page under Documentation > Cisco IOS Software > 12.2 Mainline > 
Command References.

This chapter consists of these sections:

With fallback bridging, the switch bridges together two or more VLANs or routed ports, essentially 
connecting multiple VLANs within one bridge domain. Fallback bridging forwards traffic that the switch 
does not route and forwards traffic belonging to a nonroutable protocol such as DECnet.

A VLAN bridge domain is represented with switch virtual interfaces (SVIs). A set of SVIs and routed 
ports (which do not have any VLANs associated with them) can be configured (grouped together) to 
form a bridge group. Recall that an SVI represents a VLAN of switch ports as one interface to the routing 
or bridging function in the system. You associate only one SVI with a VLAN, and you configure an SVI 
for a VLAN only when you want to route between VLANs, to fallback-bridge nonroutable protocols 
between VLANs, or to provide IP host connectivity to the switch. A routed port is a physical port that 
acts like a port on a router, but it is not connected to a router. A routed port is not associated with a 
particular VLAN, does not support VLAN subinterfaces, but behaves like a normal routed port. For more 
information about SVIs and routed ports, see 

A bridge group is an internal organization of network interfaces on a switch. You cannot use bridge 
groups to identify traffic switched within the bridge group outside the switch on which they are defined. 
Bridge groups on the switch function as distinct bridges; that is, bridged traffic and bridge protocol data 
units (BPDUs) are not exchanged between different bridge groups on a switch.