Managing The Mac Address Tables - Cisco NM-8B-U - HW ROUTERS L-M User Manual

16- and 36-Port Ethernet Switch Module for Cisco 2600 Series, Cisco 3600 Series, and Cisco 3700 Series

Managing the MAC Address Tables

This section describes how to manage the MAC address tables on the Ethernet switch network module.
The following topics are included:
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•
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The switch uses the MAC address tables to forward traffic between ports. All MAC addresses in the
address tables are associated with one or more ports. These MAC tables include the following types of
addresses:
•
•
•
The address tables list the destination MAC address and the associated VLAN ID, module, and port
number associated with the address. The following shows an example of a list of addresses as they would
appear in the dynamic, secure, or static address table.
Router# show mac
4d01h:%SYS-5-CONFIG_I:Configured from console by consolec
Slot # :0
--------------
Destination Address
-------------------
0004.272f.49de
0004.2762.3235
0004.4d07.6960
0004.ddbb.6700
0020.18d7.4304
beef.beef.beef
0004.2762.3235
0004.ddbb.6700
0002.7e48.cc38
Understanding MAC Addresses and VLANs
All addresses are associated with a VLAN. An address can exist in more than one VLAN and have
different destinations in each. Multicast addresses, for example, could be forwarded to port 1 in VLAN
1 and ports 9, 10, and 11 in VLAN 5.
Each VLAN maintains its own logical address table. A known address in one VLAN is unknown in
another until it is learned or statically associated with a port in the other VLAN. An address can be secure
in one VLAN and dynamic in another. Addresses that are statically entered in one VLAN must be static
addresses in all other VLANs.
Understanding MAC Addresses and VLANs, page 115
Changing the Address Aging Time, page 116
Configuring the Aging Time, page 116
Dynamic address—a source MAC address that the switch learns and then drops when it is not in use.
Secure address—a manually entered unicast address that is usually associated with a secured port.
Secure addresses do not age.
Static address—a manually entered unicast or multicast address that does not age and that is not lost
when the switch resets.
Address Type
------------
Dynamic
Dynamic
Dynamic
Self
Dynamic
Static
Dynamic
Self
Dynamic
0002.7e48.cc39
VLAN Destination Port
---- --------------------
1 FastEthernet0/8
1 FastEthernet0/3
1 FastEthernet0/0
1 Vlan1
1 FastEthernet0/2
1 FastEthernet0/11
2 FastEthernet0/3
2 Vlan2
3 FastEthernet0/4
Dynamic 3 FastEthernet0/5
Cisco IOS Release 12.2(2)XT, 12.2(8)T, and 12.2(15)ZJ
Configuration Tasks
115