Software Configuration Guide, Cisco IOS Release 15.2(6)E (Catalyst Digital Building Series Switches)
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Configuring the MAC
Address-Table Move Update Feature
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Information About
MAC Address-Table Move Update
MAC Address-Table Move Update
The MAC address-table move
update feature allows the
device to provide rapid bidirectional
convergence when a primary (forwarding) link goes down and the standby link
begins forwarding traffic.
Figure 1. MAC Address-Table Move Update
Example. In the following
figure, switch A is an access switch, and ports 1 and 2 on switch A are
connected to uplink
devices B and D through a Flex Links pair.
Port 1 is forwarding traffic, and port 2 is in the backup state. Traffic from
the PC to the server is forwarded from port 1 to port 3. The MAC address of the
PC has been learned on port 3 of
device C. Traffic from the server to the PC
is forwarded from port 3 to port 1.
If the MAC address-table move
update feature is not configured and port 1 goes down, port 2 starts forwarding
traffic. However, for a short time,
device C keeps forwarding traffic from the
server to the PC through port 3, and the PC does not get the traffic because
port 1 is down. If
device C removes the MAC address of the PC on
port 3 and relearns it on port 4, traffic can then be forwarded from the server
to the PC through port 2.
If the MAC address-table move
update feature is configured and enabled on the
devices, and port 1 goes down, port 2 starts
forwarding traffic from the PC to the server. The
device sends a MAC address-table move update
packet from port 2.
Device C gets this packet on port 4 and
immediately learns the MAC address of the PC on port 4, which reduces the
reconvergence time.
You can configure the access
device,
device A, to
send MAC address-table
move update messages. You can also configure the uplink
devices B, C, and D to
get and process
the MAC address-table move update messages. When
device C gets a MAC address-table move update
message from
device A,
device C learns the MAC address of the PC on
port 4.
Device C updates the MAC address table,
including the forwarding table entry for the PC.
Device A does not need to wait for the MAC
address-table update. The
device detects a failure on port 1 and
immediately starts forwarding server traffic from port 2, the new forwarding
port. This change occurs in less than 100 milliseconds (ms). The PC is directly
connected to
device A, and the connection status does not
change.
Device A does not need to update the PC entry
in the MAC address table.
MAC Address-Table Move Update Configuration Guidelines
You can enable and configure this feature on the access device to send the MAC address-table move updates.
You can enable and configure this feature on the uplink devices to get the MAC address-table move updates.
Specifies the
interface, and enters interface configuration mode. The interface can be a
physical Layer 2 interface or a port channel (logical interface).
The port-channel range is 1
to 24.
Configures a
physical Layer 2 interface (or port channel), as part of a Flex Links pair with
the interface. The MAC address-table move update VLAN is the lowest VLAN ID on
the interface.
Configure a
physical Layer 2 interface (or port channel) and specifies the VLAN ID on the
interface, which is used for sending the MAC address-table move update.
When one link is
forwarding traffic, the other interface is in standby mode.
Step 4
end
Example:
Device(config-if)# end
Returns to global
configuration mode.
Step 5
mac address-table
move update transmit
Example:
Device(config)#
mac address-table move update
transmit
Enables the access
device to send MAC address-table move updates
to other
devices in the network if the primary link
goes down and the
device starts forwarding traffic through the
standby link.
Enter command mac address-table move update on the device, for MMU packets to update MAC tables. When the primary link comes back up, the MAC tables need to reconverge and this command
will transmit the MMU, that will establish the behavior.
Step 6
end
Example:
Device(config)# end
Returns to
privileged EXEC mode.
Configuring a Device to Obtain and Process MAC Address-Table Move Update Messages
SUMMARY STEPS
configure terminal
mac address-table move update receive
end
DETAILED STEPS
Command or Action
Purpose
Step 1
configure terminal
Example:
Device# configure terminal
Enters global configuration mode
Step 2
mac address-table move update receive
Example:
Device (config)# mac address-table move update receive
Enables the device to obtain and processes the MAC address-table move updates.
Step 3
end
Example:
Device (config)# end
Returns to privileged EXEC mode.
Monitoring the MAC
Address-Table Move Update
Command
Purpose
show mac address-table move
update
Displays the MAC
address-table move update information on the
device.
Configuration
Examples for MAC Address-Table Move Update
Configuring the MAC Address-Table Move Update: Examples
This example shows how to verify the configuration after you configure an access device to send MAC address-table move updates:
Device# show mac address-table move update
Switch-ID : 010b.4630.1780
Dst mac-address : 0180.c200.0010
Vlans/Macs supported : 1023/8320
Default/Current settings: Rcv Off/On, Xmt Off/On
Max packets per min : Rcv 40, Xmt 60
Rcv packet count : 5
Rcv conforming packet count : 5
Rcv invalid packet count : 0
Rcv packet count this min : 0
Rcv threshold exceed count : 0
Rcv last sequence# this min : 0
Rcv last interface : Po2
Rcv last src-mac-address : 000b.462d.c502
Rcv last switch-ID : 0403.fd6a.8700
Xmt packet count : 0
Xmt packet count this min : 0
Xmt threshold exceed count : 0
Xmt pak buf unavail cnt : 0
Xmt last interface : None
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