54 Cisco LAN Switching Configuration Handbook
An entry for the destination MAC address mac-addr (dotted-triplet format) is made
to point to one or more switch interfaces. If the destination port is a trunk, you must
also specify the destination VLAN number vlan-id.
Switching table entries can be static (not subject to aging), dynamic (entries are
aged), or secure.
Note You can use the port security feature to restrict input to an interface by limiting
and identifying MAC addresses of the workstations that are allowed to access the port.
When you assign secure MAC addresses to a secure port, the port does not forward pack-
ets with source addresses outside the group of defined addresses. If you limit the number
of secure MAC addresses to one and assign a single secure MAC address, the workstation
attached to that port is assured the full bandwidth of the port.
2. (Optional) Set the switching table aging time:
(global) mac-address-table aging-time seconds [vlan vlan-id]
For VLAN number vlan-id (2 to 1001), entries are aged out of the switching table
after seconds (0, 10 to 1,000,000 seconds; default 300 seconds). A value of 0 dis-
ables the aging process. The VLAN number is optional. If not specified, the aging
time is modified for all VLANs.
3. (Optional) Remove a switching table entry:
(global) no mac-address-table static mac-addr {vlan vlan-id} [interface int1
[int2 ... int15] [protocol {ip | ipx | assigned}]
You can remove an entry by referencing its MAC address mac-addr. If it is defined
on more than one VLAN, the vlan-id must also be given. Switches allow the specific
destination interfaces to be given, along with a specific protocol.
Displaying Information About the Switching Table
Table 4-1 lists some switch commands that you can use to display helpful information
about the Layer 2 switching table contents.
Switching Table Example
Suppose you need to locate the switch port where a specific PC is connected. The PC’s
MAC address is 00-b0-d0-f5-45-0e:
(exec) show mac-address-table address 00b0.d0f5.450e
An IOS switch can have this output:
switch-ios# show mac-address-table address 00b0.d0f5.450e
Non-static Address Table:
Destination Address Address Type VLAN Destination Port
————————— —————— —— ——————————
00d0.b7e5.4dc3 Dynamic 534 FastEthernet0/2
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