Software Configuration Guide, Cisco IOS Release 15.2(5)EX (Cisco Digital Building Switches)
Bias-Free Language
The documentation set for this product strives to use bias-free language. For the purposes of this documentation set, bias-free is defined as language that does not imply discrimination based on age, disability, gender, racial identity, ethnic identity, sexual orientation, socioeconomic status, and intersectionality. Exceptions may be present in the documentation due to language that is hardcoded in the user interfaces of the product software, language used based on RFP documentation, or language that is used by a referenced third-party product. Learn more about how Cisco is using Inclusive Language.
Configuring the MAC
Address-Table Move Update Feature
Finding Feature
Information
Your software release
may not support all the features documented in this module. For the latest
caveats and feature information, see Bug Search Tool and the release notes for
your platform and software release. To find information about the features
documented in this module, and to see a list of the releases in which each
feature is supported, see the feature information table at the end of this
module.
Use Cisco Feature
Navigator to find information about platform support and Cisco software image
support. To access Cisco Feature Navigator, go to
http://www.cisco.com/go/cfn.
An account on Cisco.com is not required.
Information About
MAC Address-Table Move Update
MAC Address-Table Move Update
The MAC address-table move
update feature allows the
switch 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
switches 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
switch 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,
switch 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
switch 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
switches, and port 1 goes down, port 2 starts
forwarding traffic from the PC to the server. The
switch sends a MAC address-table move update
packet from port 2.
Switch 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
switch,
switch A, to
send MAC address-table
move update messages. You can also configure the uplink
switches B, C, and D to
get and process
the MAC address-table move update messages. When
switch C gets a MAC address-table move update
message from
switch A,
switch C learns the MAC address of the PC on
port 4.
Switch C updates the MAC address table,
including the forwarding table entry for the PC.
Switch A does not need to wait for the MAC
address-table update. The
switch 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
switch A, and the connection status does not
change.
Switch 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 switch to send the MAC address-table move updates.
You can enable and configure this feature on the uplink switches 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:
Switch(config-if)# end
Returns to global
configuration mode.
Step 5
mac address-table
move update transmit
Example:
Switch(config)#
mac address-table move update
transmit
Enables the access
switch to send MAC address-table move updates
to other
switches in the network if the primary link
goes down and the
switch starts forwarding traffic through the
standby link.
Step 6
end
Example:
Switch(config)# end
Returns to
privileged EXEC mode.
Configuring a Switch 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:
Switch# configure terminal
Enters global configuration mode
Step 2
mac address-table move update receive
Example:
Switch (config)# mac address-table move update receive
Enables the switch to obtain and processes the MAC address-table move updates.
Step 3
end
Example:
Switch (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
switch.
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 switch to send MAC address-table move updates:
Switch# 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
Feedback