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Cisco IE 2000 Switch Software Configuration Guide
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Chapter 24 Configuring FlexLinks and the MAC Address-Table Move Update
Information About Configuring the FlexLinks and the MAC Address-Table Move Update
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 FlexLinks interfaces.
In Figure 24-1, ports 1 and 2 on switch A are connected to uplink switches B and C. Because they are
configured as FlexLinks, only one of the interfaces is forwarding t raffic; 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 Figure 24-1, you can configure the FlexLinks pair with
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 24-1 FlexLinks Configuration Example
If a primary (forwarding) link goes down, a trap notifies the network ma nagement stations. If the standby
link goes down, a trap notifies the users.
FlexLinks are supported only on Layer 2 ports and port chan nels, not on VLANs or on Layer 3 ports.
VLAN FlexLinks Load Balancing and Support
VLAN FlexLinks load-balancing allows you to configure a FlexLinks pair so that both ports
simultaneously forward the traffic for some mutually exclusive VLANs. For example, if FlexLinks ports
are configured for 1 to100 VLANs, the traffic of the first 50 VLANs can be forwarded on one port and
the rest on the other port. If one of the ports fail, the other active port forwards all the traffic. When the
failed port comes back up, it resumes forwarding traffic in the preferred VLANs. This way, apart from
providing the redundancy, this FlexLinks pair can be used for load balancing. FlexLinks VL AN load
balancing does not impose any restrictions on uplink switches.
Switch A
Uplink
switch B
Port 1 Port 2
Uplink
switch C
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