Cabletron Systems NB20E - Manual (Page 10)

INTRODUCTION
1-4
Figure 1-1 Bridging Method
In this example, when Node A sends a packet to Node B, the bridge learns
Node A’s source address and adds the address to the Source Address
Table, indicating that the node is on LAN 1. If Node C subsequently sends
a packet to Node A, Node A’s address will be detected in the Source
Address Table for LAN 1 and the packet will not be forwarded across the
bridge to LAN 2. At the same time, the bridge will learn Node C’s source
address and add it to the Source Address Table, indicating that the node is
on LAN 1.
If the destination address of a packet is located on a different segment, the
bridge will forward the packet across the bridge. If Node B sends a packet
to Node A, the bridge will compare the destination address of the packet
against the addresses in the Source Address Table. It will then detect Node
A as being on the other side of the bridge and forward the packet through
the bridge to LAN 1. The bridge will store the address of Node B to
indicate that Node B is on LAN 2.
If no packets are sent from a source address in a five minute interval, that
address will be deleted from the bridge’s Source Address Table.
T T
T T
NODE A NODE C
LAN 1
LAN 2
NODE B