Managing The Layer 2 Forwarding Database; Types Of Forwarding Database Entries; How Entries Enter The Forwarding Database; Displaying Forwarding Database Information - Nortel 2360 Configuration Manual

Managing the layer 2 forwarding database

A WSS 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 WSS searches the
forwarding database for the packet's destination MAC address, then forwards the packet out the port associ-
ated with the MAC address.

Types of forwarding database entries

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 WSS 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 WSS 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.

How entries enter the forwarding database

An entry enters the forwarding database in one of the following ways:
• Learned from traffic received by the WSS —When the WSS 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 WSS itself—For example, the authentication protocols can add entries for wired and
wireless authentication users. The WSS also adds any static entries added by the system administrator and
saved in the configuration file.

Displaying forwarding database information

You can display the forwarding database size and the entries contained in the database.

Displaying the size of the forwarding database

To display the number of entries contained in the forwarding database, use the following command:
show fdb count {perm | static | dynamic} [vlan vlan-id]
Configuring and managing ports and VLANs 111
Nortel WLAN—Security Switch 2300 Series Configuration Guide