Service Manual

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 o 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 congure 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 aected.
Dell Networking OS Behavior: If you do not congure the dynamic option, the systems do not detect station moves in which a
MAC address learned o of a MAC-limited port is learned on another port on same line card. Therefore, Dell Networking OS does not
take any congured 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 congured the violation
action.
mac learning-limit mac-address-sticky
Using sticky MAC addresses allows you to associate a specic port with MAC addresses from trusted devices. If you enable sticky
MAC, the specied port retains any dynamically-learned addresses and prevents them from being transferred or learned on other
ports.
If you congure 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 conguration le that can be used as a startup conguration le, use the write config
command. If the number of existing MAC addresses is fewer than the congured mac learn limit, any additional MAC addresses are
converted to sticky MACs on that interface. To remove all sticky MAC addresses from the running cong le, disable sticky MAC and
use the write config command.
When you enable sticky mac on an interface, dynamically-learned MAC addresses do not age, even if you enabled mac-learning-
limit dynamic. If you congured mac-learning-limit and mac-learning-limit dynamic and you disabled sticky
MAC, any dynamically-learned MAC addresses ages.
mac learning-limit station-move
The station-move option, allows a MAC address already in the table to be learned o 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.
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Layer 2