Cabletron Systems SSR-ATM29-02, User Manual, Page: 63 / 386

CoreWatch User’s Guide 63
Chapter 6
Configuring SSR
Bridging
The SSR provides bridging functions. This chapter
• provides an overview of bridging on an SSR.
• discusses configuring the bridging mode of ports. A port’s bridging mode determines
the contents of that port’s Layer-2 lookup table.
• discusses controlling the aging state of SSR bridging. The SSR’s aging state determines
how long the SSR stores the MAC address information.
• explains setting up the SSR for the Spanning Tree Protocol (STP), which the SSR uses
to work around loops.
A Look at Bridging on the SSR
The SSR uses transparent bridging to link together different segments of an Ethernet
network.
In transparent bridging, the SSR operates as a learning bridge. As such, it monitors traffic
on subnetworks to learn about destination locations, down bridges, traffic congestion, and
other network information. This frees packets from having to carry routing information
and permits the SSR to forward packets based on current network conditions.
As a learning bridge, the SSR stores the source MAC address of each packet it receives.
This permits the SSR to forward future packets destined for a MAC address to be
forwarded to the port on which the source address was found. It does not forward those
packets to other ports, and thus reduces traffic on the network. If the SSR does not
recognize a packet’s MAC address, however, it forwards that packet to every port.