Reference Guide

412 | Layer 2
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To set a MAC learning limit on an interface:
Three options are available with the mac learning-limit command: dynamic, no-station-move, and
station-move.
mac learning-limit dynamic
The MAC address table is stored on the Layer 2 FIB region of the CAM (and the Layer 2 ACL region on
the E-Series). On the C-Series and S-Series the Layer 2 FIB region allocates space for static MAC address
entries and dynamic MAC address entries (all MAC address entries on the E-Series are dynamic). When
MAC Learning Limit is enabled, 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.
mac learning-limit station-move
mac learning-limit station-move is available only on platforms: c s
The station-move option, allows a MAC address already in the table to be learned off of another interface.
For example, if you disconnect a network device from one interface and reconnect it to another interface,
the MAC address is learned on the new interface. When the system detects this “station move,” the system
clears the entry learned on the original interface, and installs a new entry on the new interface.
Task Command Syntax Command Mode
Specify the number of MAC addresses that the system
can learn off a Layer 2 interface.
mac learning-limit address_limit INTERFACE
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.
FTOS Behavior: If you do not configure the dynamic option, the C-Series and S-Series 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 linecard (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.