HP 200 Series Services And Applications page 58

Bridging Service
Transparent Bridging
For example, in figure 1, the red and white LANs are connected by two
routers serving as parallel bridges, bridge 1 and bridge 2. Consider the chain
of events when end node J on the red LAN first sends a frame to end node K
on the white LAN. The frame originated by end node J and addressed to end
node K is read by both bridge 1 and bridge 2. As this is the first frame
between J and K, the address table of neither bridge contains an entry for J
or K.
Interface 1
Figure 1. Parallel Bridge Topology
Each bridge updates its address table to indicate that J is in the direction of
the red LAN. After updating its address table, each bridge floods the frame:
bridge 1 relays the frame over interface 1 and bridge 2 relays the frame over
interface 2. Bridge 2 also relays the frame over interface 3; to simplify the
example, however, this frame will not be traced.
2-6
4
White LAN
Node K
1
Red LAN
Node J
Black LAN
3
Interface 2
2
Interface 3
Blue LAN