Mac Address-Table Move Update - Cisco 3020 - Catalyst Blade Switch Configuration Manual

Understanding Flex Links and the MAC Address-Table Move Update
only one of the interfaces is in the linkup state and forwarding traffic. If the primary link shuts down,
the standby link starts forwarding traffic. When the active link comes back up, it goes into standby mode
and does not forward traffic. STP is disabled on Flex Link interfaces.
In Figure
configured as Flex Links, only one of the interfaces is forwarding traffic; the other is in standby mode.
If port 1 is the active link, it begins forwarding traffic between port 1 and switch B; the link between
port 2 (the backup link) and switch C is not forwarding traffic. If port 1 goes down, port 2 comes up and
starts forwarding traffic to switch C. When port 1 comes back up, it goes into standby mode and does
not forward traffic; port 2 continues forwarding traffic.
You can also choose to configure a preemption mechanism, specifying the preferred port for forwarding
traffic. For example, in the example in
preemption mode. In the scenario shown, when port 1 comes back up and has more bandwidth than port
2, port 1 begins forwarding traffic after 60 seconds. Port 2 becomes the standby port. You do this by
entering the interface configuration switchport backup interface preemption mode bandwidth and
switchport backup interface preemption delay commands.
Figure 16-1
Uplink
switch B
If a primary (forwarding) link goes down, a trap notifies the network management stations. If the standby
link goes down, a trap notifies the users.
Flex Links are supported only on Layer 2 ports and port channels, not on VLANs.

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.
In Figure
switches B and D through a Flex Link 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 in
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.
Cisco Catalyst Blade Switch 3020 for HP Software Configuration Guide
16-2
Chapter 16
16-1, ports 1 and 2 on switch A are connected to uplink switches B and C. Because they are
Flex Links Configuration Example
Port 1
Switch A
16-2, switch A is an access switch, and ports 1 and 2 on switch A are connected to uplink
Configuring Flex Links and the MAC Address-Table Move Update Feature
Figure 16-1, you can configure the Flex Links pair with
Uplink
switch C
Port 2
Figure 16-2
OL-8915-01