Reference Guide

In this case, the configuration is still present in the running-config and show output. Remove the configuration
before re-applying a MAC learning limit with a lower value. Also, ensure that you can view the Syslog messages on your
session.
NOTE: The CAM-check failure message beginning in FTOS version 8.3.1.0 is different from versions 8.2.1.1 and
earlier, which read:
% Error: ACL returned error
% Error: Remove existing limit configuration if it was configured before
Setting the MAC Learning Limit
To set a MAC learning limit on an interface, use the following command.
• Specify the number of MAC addresses that the system can learn off a Layer 2 interface.
INTERFACE mode
mac learning-limit address_limit
Three options are available with the mac learning-limit command:
– dynamic
– no-station-move
– station-move
NOTE: An SNMP trap is available for mac learning-limit station-move. No other SNMP traps are
available for MAC Learning Limit, including limit violations.
mac learning-limit Dynamic
The MAC address table is stored on the Layer 2 forwarding information base (FIB) region of the CAM.
The Layer 2 FIB region allocates space for static MAC address entries and dynamic MAC address entries. When you
enable MAC learning limit, entries created on this port are static by default. When you configure the dynamic option,
learned MAC addresses are stored in the dynamic region and are subject to aging. Entries created before this option is
set are not affected.
FTOS Behavior: If you do not configure the dynamic option, the systems do not detect station moves in which a MAC
address learned off of a MAC-limited port is learned on another port on same line card. Therefore, FTOS does not take
any configured station-move violation action. When a MAC address is relearned on any other line card (any line card
except the one to which the original MAC-limited port belongs), the station-move is detected and the system takes the
configured the violation action.
mac learning-limit mac-address-sticky
Using sticky MAC addresses allows you to associate a specific port with MAC addresses from trusted devices. If you
enable sticky MAC, the specified port retains any dynamically-learned addresses and prevents them from being
transferred or learned on other ports.
If you configure mac-learning-limit and you enabled sticky MAC, all dynamically-learned addresses are
converted to sticky MAC addresses for the selected port. Any new MAC addresses learned on this port is converted to
sticky MAC addresses.
To save all sticky MAC addresses into a configuration file that can be used as a startup configuration file, use the
write config command. If the number of existing MAC addresses is fewer than the configured mac learn limit, any
additional MAC addresses are converted to sticky MACs on that interface. To remove all sticky MAC addresses from the
running config file, disable sticky MAC and use the write config command.
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