3com WX2200 3CRWX220095A User Manual

C

HAPTER

 5: C

ONFIGURING

 

AND

 M

ANAGING

 P

ORTS

 

AND

 VLAN

S

A WX switch uses a Layer 2 forwarding database (FDB) to forward traffic 
within a VLAN. The entries in the forwarding database map MAC 
addresses to the physical or virtual ports connected to those MAC 
addresses within a particular VLAN. To forward a packet to another 
device in a VLAN, the WX switch searches the forwarding database for 
the packet’s destination MAC address, then forwards the packet out the 
port associated with the MAC address.

The forwarding database can contain the following types of entries:

„

Dynamic — A dynamic entry is a temporary entry that remains in the 
database only until the entry is no longer used. By default, a dynamic 
entry ages out if it remains unused for 300 seconds (5 minutes). All 
dynamic entries are removed if the WX switch is powered down or 
rebooted.

„

Static — A static entry does not age out, regardless of how often the 
entry is used. However, like dynamic entries, static entries are removed 
if the WX switch is powered down or rebooted.

„

Permanent — A permanent entry does not age out, regardless of 
how often the entry is used. In addition, a permanent entry remains in 
the forwarding database even following a reboot or power cycle. 

An entry enters the forwarding database in one of the following ways:

„

Learned from traffic received by the WX switch — When the WX 
switch receives a packet, the switch adds the packet’s source MAC 
address to the forwarding database if the database does not already 
contain an entry for that MAC address.

„

Added by the system administrator — You can add static and 
permanent unicast entries to the forwarding database. (You cannot 
add a multicast or broadcast address as a permanent or static 
forwarding database entry.)

„

Added by the WX switch itself — For example, the authentication 
protocols can add entries for wired and wireless authentication users. 
The WX switch also adds any static entries added by the system 
administrator and saved in the configuration file.