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Cisco Systems IntelligentGigabit Ethernet Switch Modules for the IBMBladeCenter, Software Configuration Guide
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Chapter24 Configuring EtherChannels and Layer2 Trunk Failover
Configuring Layer 2 Trunk Failover
The link state of the downstream interfaces depend on the link state of the upstream interfaces in the
associated link-state group. If all of the upstream interfaces in a link-state group are in a link-down state,
then the associated downstream interfaces are forced into a link-down state. If any one of the upstream
interfaces in the link-state group is in a link-up state, the associated downstream interfaces are allowed
to change to, or remain in, a link-up state.
In Figure 24-4, downstream interfaces 1, 2, and 3 are in link-state group 1 with upstream interfaces 17
and 18. Similarly, downstream interfaces 4, 5, and 6 are in link-state group 2 with upstream interfaces
19 and 20.
If link is lost on upstream interface 17, the link state of downstream interfaces 1 to 3 do not change. If
upstream interface 18 also loses link, downstream interfaces 1 to 3 go into a link-down state.
Downstream interfaces 4 to 6 do not change state.
You can recover a downstream interface link-down condition by removing the failed downstream port
from the link-state group. You can also enable one of the upstream interfaces in the group to change to
the link-up state. To recover multiple downstream interfaces, disable the link-state group.
Figure24-4 Typical Layer 2 Trunk Failover Configuration
Configuring Layer 2 Trunk Failover
These sections describe how to configure trunk failover ports:
•Default Layer 2 Trunk Failover Configuration, page 24-16
•Layer 2 Trunk Failover Configuration Guidelines, page 24-17
•Configuring Layer 2 Trunk Failover, page 24-17

Default Layer 2 Trunk Failover Configuration

There are no link-state groups defined, and trunk failover is not ena bled for any group.
BladeCenter For example
Catalyst 3550 Switch
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Downstream interface 1 Link-state group 1
Upstream interface 17
Upstream interface 18
Link-state group 2
Upstream interface 19
Upstream interface 20
Cisco
ESM
Downstream interface 2
Downstream interface 3
Downstream interface 4
Downstream interface 5
Downstream interface 6
Network