Chapter 2Chapter 2 Bridging Configuration GuideBridging OverviewThe SmartSwitch Router provides the following bridging functions:• Complies with the IEEE 802.1d standard• Complies with the IGMP multicast bridging standard• Provides wire-speed address-based bridging or flow-based bridging• Provides the ability to logically segment a transparently bridged network into virtuallocal-area networks (VLANs) based on physical ports or protocol (IP or IPX orbridged protocols like Appletalk)• Allows frame filtering based on MAC address for bridged and multicast traffic• Provides integrated routing and bridging, which supports bridging of intra-VLANtraffic and routing of inter-VLAN trafficSpanning Tree (IEEE 802.1d)Spanning tree (IEEE 802.1d) allows bridges to dynamically discover a subset of thetopology that is loop-free. In addition, the loop-free tree that is discovered containspaths to every LAN segment.Bridging Modes (Flow-Based and Address-Based)The SSR provides the following types of wire-speed bridging:Address-based bridging - The SSR performs this type of bridging by looking up thedestination address in an L2 lookup table on the line card that receives the bridgepacket from the network. The L2 lookup table indicates the exit port(s) for the bridgedpacket. If the packet is addressed to the SSR's own MAC address, the packet is routedrather than bridged.Flow-based bridging - The SSR performs this type of bridging by looking up an entryin the L2 lookup table containing both the source and destination addresses of thereceived packet in order to determine how the packet is to be handled.The SSR ports perform address-based bridging by default but can be configured toperform flow-based bridging instead, on a per-port basis. A port cannot be configuredto perform both types of bridging at the same time.The SSR performance is equivalent when performing flow-based bridging or address-based bridging. However, address-based bridging is more efficient because it requires
