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Cisco ASR 901 Series Aggregation Services Router Software Configuration Guide
OL-23826-09
Chapter 8 Configuring Ethernet Virtual Connections
Configuring Other Features on EFPs
Disabling MAC Address Learning on an Interface or Bridge Domain
By default, MAC address learning is enabled on all interfaces and bridge domains or VLANs on the
router. You can control MAC address learning on an interface or VLAN to manage the available MAC
address table space by controlling which interfaces or VLANs can learn MAC addresses. When you
disable MAC address learning for a BD/VLAN or interface, the router that receives packet from any
source on the BD, VLAN or interface, the addresses are not learned. Since addresses are not learned, all
IP packets floods into the Layer 2 domain.
Prerequisites
You can disable MAC address learning on a single VLAN ID from 2 to 4092 (for example, no
mac-address-table learning vlan 10). If the MAC address learning is disabled for a VLAN or interface,
the already learnt addresses for that VLAN or interface are immediately removed from the MAC address
table. However, you cannot disable MAC learning for the reserved 4093, 4094, and 4095 VLAN IDs. If
the VLAN ID that you enter is a reserved VLAN, the switch generates an error message and rejects the
command.
• We recommend that you disable MAC address learning only in VLANs with two ports. If you
disable MAC address learning on a VLAN with more than two ports, every packet entering the
switch is flooded in that VLAN domain.
Restrictions
• You cannot disable MAC address learning on a VLAN that is used internally by the router. VLAN
ID 1 is used internally by the router. If the VLAN ID that you enter is an internal VLAN, the switch
generates an error message and rejects the command.
Complete the following steps to disable MAC address learning on a VLAN:
SUMMARY STEPS
1. configure terminal
2. no mac-address-table learning {vlan vlan-id | interface interface slot/port}
3. end
4. copy running-config startup-config
DETAILED STEPS
Command or Action Purpose
Step 1
configure terminal
Example:
Router# configure terminal
Enters global configuration mode.
Step 2
no mac-address-table learning {vlan vlan-id |
interface type slot/port}
Example:
Router(config)# no mac-address-table learning
vlan 10
Disable MAC address learning on an interface or on a
specified VLAN.
vlan vlan-id—Specifies the VLAN ID which ranges from 2
to 4094. It cannot be an internal VLAN or reserved VLAN.
interface type slot/port—Specifies the location of the
interface and its type.