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Cisco ASA 5500 Series Configuration Guide using the CLI
Chapter 4 Configuring the Transparent or Routed Firewall
Customizing the MAC Address Table for the Transparent Firewall
Disabling MAC Address Learning
By default, each interface automatically learns the MAC addresses of entering traffic, and the ASA adds
corresponding entries to the MAC address table. You can disable MAC address learning if desired,
however, unless you statically add MAC addresses to the table, no traffic can pass through the ASA.
To disable MAC address learning, enter the following command:
Monitoring the MAC Address Table
You can view the entire MAC address table (including static and dynamic entries for both interfaces), or
you can view the MAC address table for an interface. To view the MAC address table, enter the following
command:
Examples
The following is sample output from the show mac-address-table command that shows the entire table:
hostname# show mac-address-table
interface mac address type Time Left
-----------------------------------------------------------------------
outside 0009.7cbe.2100 static -
inside 0010.7cbe.6101 static -
inside 0009.7cbe.5101 dynamic 10
The following is sample output from the show mac-address-table command that shows the table for the
inside interface:
hostname# show mac-address-table inside
interface mac address type Time Left
-----------------------------------------------------------------------
inside 0010.7cbe.6101 static -
Command Purpose
mac-address-table aging-time timeout_value
Example:
hostname(config)# mac-address-table
aging-time 10
Sets the MAC address entry timeout.
The timeout_value (in minutes) is between 5 and 720 (12 hours). 5 minutes
is the default.
Command Purpose
mac-learn interface_name disable
Example:
hostname(config)# mac-learn inside disable
Disables MAC address learning.
The no form of this command reenables MAC address learning. The clear
configure mac-learn command reenables MAC address learning on all
interfaces.
Command Purpose
show mac-address-table [interface_name]
Shows the MAC address table.