Cisco Catalyst 2960-XR Configuration Manual page 166

Configuring Flex Links and the MAC Address-Table Move Update Feature
MAC Address-Table Move Update
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.
Figure 27: MAC Address-Table Move Update Example
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 100
Catalyst 2960-XR Switch Layer 2 Configuration Guide, Cisco IOS Release 15.0(2)EX1
152 OL-29424-01