A bridge is a hardware device also needed to connect two LAN code segments to extend a LAN. A bridge uses two NICs to connect two code segments. It listens to all traffic and knows frame format. It also transfers only correct complete frames and removed the collided and error frames.
A typical bridge has two NICs, a CPU a storage and a ROM. It only executes the code stored in its ROM.
STARTUP AND STEADY STATE:
When a bridge first lodes the address lists are empty. The bridge forwards frames to the other code segment if it may not know its destination address in its lists.
After period of time when the bridge has accepted at least one frame from each computer, it has the lists created it forwards frames as far it is useful.
PLANNING A BRIDGE NETWORK:
In a steady state, a bridge gives simultaneous use of every segment. When designing a LAN, bridges may be installed to convert the LAN into segments to enhance performance.
For example: Frequently contacting devices may be attached to the similar segment. The frame traffic on one segment does not affect the other code segments.