Dell S4048-ON, Configuration Manual

Page: 485 / 1039

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.
Dell Networking OS Behavior : If you do not configure the
dynamic
option, the system does not detect station moves in which a
MAC address learned from a MAC-limited port is learned on another port on the same system. Therefore, any configured violation
response to detected station moves is not performed. 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.
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 configured
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
mac learning-limit station-move
command allows a MAC address already in the table to be learned from 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.
Layer 2
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