Chapter 10 Interface

10.13 Bridge Interface Screen

A bridge creates a connection between two or more network segments at the layer-2 (MAC address) level.

Unlike the device-wide bridge mode in ZyNOS-based ZyWALLs, this ZyWALL can bridge traffic between some interfaces while it routes traffic for other interfaces. The bridge interfaces also support more functions, like interface bandwidth parameters, DHCP settings, and ping check. To use the whole ZyWALL as a transparent bridge, add all of the ZyWALL’s interfaces to a bridge interface.

In the following example, bridge X connects four network segments.

Figure 180 Bridge Example

When the bridge receives a packet, the bridge records the source MAC address and the port on which it was received in a table. It also looks up the destination MAC address in the table. If the bridge knows on which port the destination MAC address is located, it sends the packet to that port. If the destination MAC address is not in the table, the bridge broadcasts the packet on every port (except the one on which it was received).

In the example above, computer A sends a packet to computer B. Bridge X records the source address 0A:0A:0A:0A:0A:0A and port 2 in the table. It also looks up 0B:0B:0B:0B:0B:0B in the table. There is no entry yet, so the bridge broadcasts the packet on ports 1, 3, and 4.

Table 76 Example: Bridge Table After Computer A Sends a Packet to Computer B

MAC ADDRESS

PORT

0A:0A:0A:0A:0A:0A

2

 

 

If computer B responds to computer A, bridge X records the source address 0B:0B:0B:0B:0B:0B and port 4 in the table. It also looks up 0A:0A:0A:0A:0A:0A in the table and sends the packet to port 2 accordingly.

Table 77 Example: Bridge Table After Computer B Responds to Computer A

MAC ADDRESS

PORT

0A:0A:0A:0A:0A:0A

2

0B:0B:0B:0B:0B:0B

4

 

255

ZyWALL USG 100/200 Series User’s Guide