Riverstone Networks WICT1-12 - Manual (Page 65)

Riverstone Networks RS Switch Router User Guide Release 8.0 5-1
5 BRIDGING CONFIGURATION GUIDE
The Riverstone RS Switch Router provides the following bridging functions:
• Compliance with the IEEE 802.1d standard
• Compliance with the IGMP multicast bridging standard
• Wire-speed address-based bridging or flow-based bridging
• Ability to logically segment a transparently bridged network into virtual local-area networks
(VLANs), based on physical ports or protocol (IP or IPX or bridged protocols like Appletalk)
• Frame filtering based on MAC address for bridged and multicast traffic
• Integrated routing and bridging, which supports bridging of intra-VLAN traffic and routing of
inter-VLAN traffic
5.1 SPANNING TREE (IEEE 802.1D)
Spanning tree (IEEE 802.1d) allows bridges to dynamically discover a subset of the topology that is loop-free. In
addition, the loop-free tree that is discovered contains paths to every LAN segment.
5.2 BRIDGING MODES (FLOW-BASED AND
ADDRESS-BASED)
The RS provides the following types of wire-speed bridging:
Address-based bridging - The RS performs this type of bridging by looking up the destination address in an L2
lookup table on the line card that receives the bridge packet from the network. The L2 lookup table indicates the
exit port(s) for the bridged packet. If the packet is addressed to the RS' own MAC address, the packet is routed
rather than bridged.
Flow-based bridging - The RS performs this type of bridging by looking up an entry in the L2 lookup table
containing both the source and destination addresses of the received packet in order to determine how the packet
is to be handled.
The RS ports perform address-based bridging by default but can be configured to perform flow-based bridging
instead, on a per-port basis. A port cannot be configured to perform both types of bridging at the same time.
The RS performance is equivalent when performing flow-based bridging or address-based bridging. However,
address-based bridging is more efficient because it requires fewer table entries while flow-based bridging provides
tighter management and control over bridged traffic.