fdb (Forwarding database)

[Netomaniac]

guys,

What is fdb used for. Where will the database be forwarded by default.

Neto...........

 

[rn4it]

It's the MAC address table, it keeps track of MAC address to interface ports on the switch.

 

[Netomaniac]

where will it be forwarded, by default.


Neto....

 

[rn4it]

The database isn't forwarded anywhere, it just keeps track of what MAC addresses are learned on what interface ports. This is for switching decisions, the exaqmple below is an exerpt from a sh fdb command. In short, what it's saying is the 00:16:41:6c:7c:cc MAC address on VLAN1 can be found on port 9 of the local switch. So if another device is looking for it, it will be forwarded out interface 9, provided is on the same VLAN or is able to be routed onto VLAN1.

example, MAC address VLAN assignment port#
1fbf0-030: 00:16:41:6c:7c:cc vlan1(2050) 0000 d m 9

This database is dynamic in that as new devices are learned on interfaces it will change. For example if I take the device that's patched into port 9 in the example above and move it to port 15. The above entry would be remove from the fdb and a new entry would be added showing it on port 15. For example
1fbf0-030: 00:16:41:6c:7c:cc vlan1(2050) 0000 d m 15

hope this helps.