ZyXEL Communications ISG50 User Manual
Chapter 12 Interfaces
ISG50 User’s Guide
268
Bridge Overview
A bridge creates a connection between two or more network segments at the layer-2 (MAC
address) level. In the following example, bridge X connects four network segments.
address) level. In the following example, bridge X connects four network segments.
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).
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.
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.
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.
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.
Bridge Interface Overview
A bridge interface creates a software bridge between the members of the bridge interface. It also
becomes the ISG50’s interface for the resulting network.
becomes the ISG50’s interface for the resulting network.
The ISG50 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 connectivity check. To use the whole ISG50 as a transparent bridge, add all of the ISG50’s
interfaces to a bridge interface.
bridge interfaces also support more functions, like interface bandwidth parameters, DHCP settings,
and connectivity check. To use the whole ISG50 as a transparent bridge, add all of the ISG50’s
interfaces to a bridge interface.
A bridge interface may consist of the following members:
Table 74
Example: Bridge Table After Computer A Sends a Packet to Computer B
MAC ADDRESS
PORT
0A:0A:0A:0A:0A:0A
2
Table 75
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