- Audience
- Getting Started with Cisco ME 2600X
- Ethernet Virtual Circuit
- Quality of Service
- Resilient Ethernet Protocol
- Link Aggregation Group and Link Aggregation Control Protocol
- MAC Learning
- Multicast VLAN Registration
- IGMP Snooping
- Remote Network Monitoring and Alarm Troubleshooting
- Authentication, Authorization, and Accounting (AAA)
- Cisco Discovery Protocol
- SNMP
- IP Source Guard for Service Instance
- DHCP Snooping
- Dynamic ARP Inspection
- MAC Address Security
- Layer 2 Access Control Lists on EVCs
- Layer 3 Access Control Lists on EVCs
- Storm Control over EVC
- Control Plane Policing
- ICMP Unreachable Rate Limiting User Feedback
- IP Version 6 Support for the Management Port
- SSH
- PPPoE Intermediate Agent
- CFM over EVC
- Index
Cisco ME 2600X Series Ethernet Access Switch Software Configuration Guide
- Updated:
- September 3, 2014
Chapter: MAC Learning
MAC Learning
This chapter describes MAC learning, MAC address limiting, and static MAC address. This chapter also describes the configuration procedures.
- Understanding MAC Learning
- Understanding MAC Address Limiting
- Understanding the Static MAC Address
- Removing a MAC Address
- Displaying Information About the MAC Address Table
Understanding MAC Learning
A software MAC address table is maintained on the Cisco ME 2600X. This MAC address table contains the MAC addresses learned on all the interfaces of Cisco ME 2600X.
 Note | By default, MAC address learning is enabled only for point–to–multipoint bridge domains and can also be disabled. |
MAC Address Aging
Dynamically learned MAC addresses are deleted after the MAC address age out value. This frees up unused addresses from the MAC address table for other active subscribers. In Cisco ME 2600X, the default value for MAC address aging is 300 seconds and cannot be changed. The expected MAC address age out timer is between 300 to 600 seconds depending on the number of MAC addresses learned.
Dynamic MAC Address Learning
Dynamic MAC address learning occurs when the bridging data path encounters an ingress frame whose source address is not present in the MAC address table for the ingress service instance. The learned MAC addresses are distributed to the other cards with Ethernet Flow Points (EFPs) in the same bridge domain.
MAC Move
A MAC move occurs when the same MAC address is re-learned on a different port. When a MAC move is detected, a transient event is generated to inform the user about the MAC move.
MAC Learning on LAG
MAC learning is enabled on the LAG interface, if the Link Aggregation Group (LAG) interface is part of the point–to–multipoint bridge domain. The MAC addresses are learned on the LAG interface instead of the physical interface.
- MAC Learning Actions
- MAC Learning Configuration Procedures
- Re–enabling or Disabling MAC Learning on a Bridge Domain
MAC Learning Actions
The table below describes the various scenarios and the actions taken on MAC addresses for each scenario.
| Scenario | Action |
|---|---|
| A bridge domain is created. | The MAC learning is enabled by default in point–to–multipoint bridge domains. The MAC learning is not supported in point–to–point bridge domains. |
| A bridge domain is deleted. | The MAC addresses learned on the bridge domain are removed from the software MAC address table that is maintained on the interface on Cisco ME 2600X. |
| An EFP is added and is the first EFP on a bridge domain on an interface of Cisco ME 2600X. | All the MAC addresses learned on the bridge domain are sent to this new interface on Cisco ME 2600X. |
| An EFP is added and is not the first EFP on a bridge domain. | Nothing needs to be done as the MAC addresses learned on the bridge domain are already present. |
| An EFP is deleted. | All the MAC addresses learned on that EFP are deleted. |
| An EFP admin state is UP. | When the EFP is the first EFP on the bridge domain on the Cisco ME 2600X, all the MAC addresses learned on the bridge domain are sent to this new interface on Cisco ME 2600X. When the EFP is not the first EFP on the bridge domain on the interface, nothing needs to be done as the MAC addresses learned on the bridge domain are already present. |
| An EFP admin state is DOWN. | All the MAC addresses learned on that EFP are deleted. |
| The port goes down. | All the MAC addresses learned on the port on all the bridge domains are deleted. |
MAC Learning Configuration Procedures
The following procedures can be performed using Cisco IOS commands to configure MAC learning and MAC address limiting:
Re–enabling or Disabling MAC Learning on a Bridge Domain
Note | MAC learning is enabled on the point–to–multipoint bridge domains by default. |
1.
enable
2.
configure terminal
3.
bridge-domain bridge-id
4.
mac learning
5.
no mac learning
6.
end
DETAILED STEPS
Example: Re–enable or Disable MAC Learning on a Bridge Domain
The following example shows how to re-enable MAC learning on a bridge domain using Cisco IOS commands:
Switch> enable Switch# configure terminal Switch(config)# bridge-domain 100 Switch(config-bdomain)# mac learning Switch(config-bdomain)# end
The following example shows how to disable MAC learning on a bridge domain using Cisco IOS commands:
Switch> enable Switch# configure terminal Switch(config)# bridge-domain 100 Switch(config-bdomain)# no mac learning Switch(config-bdomain)# end
Understanding MAC Address Limiting
The MAC Address Limiting for bridge domains provides the capability to control the MAC addresses learnt on the bridge domain. You can configure an upper limit on the number of MAC addresses that can be learnt in a bridge domain. If an Ethernet frame with an unknown MAC address is received, it is flooded in the bridge domain. The MAC address limiting commands are configured under the bridge domain.
Note | The maximum MAC address limit on a bridge domain is 32000. |
Configuring MAC Address Limit on a Bridge Domain
1.
enable
2.
configure terminal
3.
bridge-domain bridge-id
4.
mac limit maximum addresses maximum-addresses
5.
end
DETAILED STEPS
Example: Configure MAC Address Limit on a Bridge Domain
The following example shows how to configure MAC address limiting on a bridge domain using Cisco IOS commands:
Switch> enable Switch# configure terminal Switch(config)# bridge-domain 100 Switch(config-bdomain)# mac limit maximum addresses 1000 Switch(config-bdomain)# end
Understanding the Static MAC Address
You can configure static MAC addresses on a service instance. Static MAC address configuration on service instances eliminates the need for MAC address learning, which is required for traffic forwarding. Without MAC address learning, MAC address table resources can be conserved and network resources can be optimized.
Note | Static MAC address configuration does not apply to the MVR bridge domain. |
Benefits
Static MAC address support on service instances provides the following benefits:
Restrictions for Static MAC Address
Configuring a Static MAC Address on a Service Instance
Configuring an Ethernet Service Instance
Note | Use the no mac static address mac-addr command to remove the statically added unicast MAC address. |
1.
enable
2.
configure terminal
3.
interface type number
4.
service instance id ethernet [evc-id]
5.
mac static address mac-address
6.
exit
7.
end
DETAILED STEPS
| Command or Action | Purpose | |
|---|---|---|
| Step 1 | enable Example: Switch> enable
| Enables privileged EXEC mode. |
| Step 2 | configure terminal Example: Switch# configure terminal
| Enters global configuration mode. |
| Step 3 | interface type number Example: Switch(config)# interface TenGigabitEthernet 0/45
| Configures a Ten Gigabit Ethernet interface and enters interface configuration mode. |
| Step 4 | service instance id ethernet [evc-id] Example: Switch(config-if)# service instance 1 ethernet
| Configures an Ethernet service instance on an interface and enters service instance configuration mode. |
| Step 5 | mac static address mac-address Example: Switch(config-if-srv)# mac static address 0000.bbbb.cccc
| Configures a static MAC address on a service instance. |
| Step 6 | exit Example: Switch(config-if-srv)# exit
| Returns to interface configuration mode. |
| Step 7 | end Example: Switch(config-if)# end
| Returns to privileged EXEC mode. |
Example: Configure a Static MAC Address on a Service Instance
The following example shows how to configure a static MAC address on a service instance using Cisco IOS commands:
Switch> enable Switch# configure terminal Switch(config)# interface TenGigabitEthernet 0/45 Switch(config-if)# service instance 1 ethernet Switch(config-if-srv)# encapsulation dot1q 100 Switch(config-if-srv)# bridge-domain 100 Switch(config-if-srv)# mac static address 0000.bbbb.cccc Switch(config-if-srv)# exit Switch(config-if)# end
Removing a MAC Address
Note | This procedure removes only dynamically added MAC addresses. To remove the statically added MAC addresses, use the no mac static address mac-addr command. |
1.
enable
2.
configure terminal
3. clear mac-address-table [address mac-address] [interface type number] [bridge-domain bridgedomain-id]
4.
exit
DETAILED STEPS
| Command or Action | Purpose | |
|---|---|---|
| Step 1 | enable Example: Switch> enable
| Enables privileged EXEC mode. |
| Step 2 | configure terminal Example: Switch# configure terminal
| Enters global configuration mode. |
| Step 3 | clear mac-address-table [address mac-address] [interface type number] [bridge-domain bridgedomain-id] Example: Switch(config)# clear mac-address-table address 0000.bbbb.cccc interface TenGigabitEthernet 0/45 bridge-domain 100
| Removes the dynamic MAC address from the MAC address table on a bridge domain. The bridgedomain-id is the bridge domain number. |
| Step 4 | exit Example: Switch(config)# exit
| Exits global configuration mode. |
Example: Remove a MAC Address
The following example shows how to remove a MAC address from the MAC address table on a bridge domain using Cisco IOS commands:
Switch> enable Switch# configure terminal Switch(config)# clear mac-address-table address 0000.bbbb.cccc interface TenGigabitEthernet 0/45 bridge-domain 100 Switch(config)# exit
The following example shows how to remove a MAC address from the MAC address table on all the bridge domains using Cisco IOS commands:
Switch> enable Switch# configure terminal Switch(config)# clear mac-address-table address 0000.bbbb.cccc Switch(config)# exit
Displaying Information About the MAC Address Table
1.
enable
2.
show mac-address-table address mac-addr
3.
show mac-address-table bridge-domain bridge-domain-id
4.
show mac-address-table interface type number
DETAILED STEPS
| Command or Action | Purpose | |
|---|---|---|
| Step 1 | enable Example: Switch> enable
| Enables privileged EXEC mode. |
| Step 2 | show mac-address-table address mac-addr Example: Switch# show mac-address-table address 0050.3e8d.6400
| Displays information about the MAC address table for a specific MAC address. The mac-addr is a 48–bit MAC address and the valid format is H.H.H. |
| Step 3 | show mac-address-table bridge-domain bridge-domain-id Example: Switch# show mac-address-table bridge-domain 100
| Displays information about the MAC address table for a specific bridge domain. The bridge-domain-id is the bridge domain number. |
| Step 4 | show mac-address-table interface type number Example: Switch# show mac-address-table interface TenGigabitEthernet 0/45
| Displays information about the MAC address table for a specific interface. |
Example: Display Information About the MAC Address Table
The following example shows how to display the MAC address table information:
Switch# show mac-address-tableBridge Domain Index MAC Address Type Ports -------------------------------------------- 2 0000.1000.001e dynamic Te4/2 2 0000.1000.001d dynamic Te4/2 2 0000.1000.001c dynamic Te4/2 200 0050.3e8d.6400 static Te4/1 100 0050.3e8d.6400 static Te4/1 5 0050.3e8d.6400 static Te4/1 4 0050.3e8d.6400 static Te4/1 1 0050.3e8d.6400 static Te4/1
The following example shows how to display the MAC address table information for a specific MAC address:
Switch# show mac-address-table address 0000.1000.0001Bridge Domain Index MAC Address Type Ports -------------------------------------------- 2 0000.1000.0001 dynamic Te4/2
The following example shows how to display the MAC address table information for a specific bridge domain:
Switch# show mac-address-table bridge-domain 2Bridge Domain Index MAC Address Type Ports -------------------------------------------- 2 0000.1000.001e dynamic Te4/2 2 0000.1000.001d dynamic Te4/2 2 0000.1000.001c dynamic Te4/2 2 0000.1000.001b dynamic Te4/2 2 0000.1000.001a dynamic Te4/2 2 0000.1000.0019 dynamic Te4/2
The following example shows how to display the MAC address table information for a specific interface:
Switch# show mac-address-table interface tenGigabitEthernet 0/45Bridge Domain Index MAC Address Type Ports -------------------------------------------- 2 0000.1000.001e dynamic Te4/2 2 0000.1000.001d dynamic Te4/2 2 0000.1000.001c dynamic Te4/2 2 0000.1000.001b dynamic Te4/2 2 0000.1000.001a dynamic Te4/2 2 0000.1000.0019 dynamic Te4/2
The following example shows how to display the MAC address table information for a LAG interface (Po9):
Switch# show mac-address-tableBridge Domain Index MAC Address Type Ports -------------------------------------------- 2 0000.0300.0900 dynamic Te4/1 2 0000.0300.1000 dynamic Po9
Feedback