ZyXEL Communications 5 Series User Manual

 Chapter 33 Maintenance Screens

ZyWALL 5/35/70 Series User’s Guide

Figure 345   Synchronization Fail

Use this screen to configure your ZyWALL as a router or a bridge. In router mode, the 
ZyWALL functions as a router. In bridge mode, the ZyWALL functions as a transparent 
firewall (also known as a bridge firewall). 

A transparent bridge is invisible to the operation of a network in that it does not modify the 
frames it forwards. The bridge checks the source address of incoming frames on the port and 
learns MAC addresses to associate with that port. All future communications to that MAC 
address will only be sent on that port.

The bridge gradually builds a host MAC-address-to-port mapping table such as in the 
following example, during the learning process. 

For example, if a bridge receives a frame via port 1 from host A (MAC address 
00a0c5123478), the bridge associates host A with port 1. When the bridge receives another 
frame on one of its ports with destination address 00a0c5123478, it forwards the frame 
directly through port 1 after checking the internal table. 

The bridge takes one of these actions after it checks the destination address of an incoming 
frame with its internal table:

• If the table contains an association between the destination address and any of the bridge's 

ports aside from the one on which the frame was received, the frame is forwarded out the 
associated port.

Table 201   MAC-address-to-port Mapping Table

00a0c5123456

3

00a0c5123478 (host A) 1

00a0c512349a

3

00a0c51234bc

2

00a0c51234de

4