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Chapter 5
Using Spanning Tree with VLANs
longer, but that depends on the particular application in use. The key is not
having the application time out, and the failover time is fast enough to stop
the time-out from happening.
EtherChannel Guidelines
EtherChannel does not work under certain circumstances. This is to ensure
that no network loops will occur if the bundle comes up. There are certain
guidelines to follow when configuring EtherChannel technology:
All ports must be in the same VLAN or they must all be trunk ports.
All ports must be configured as the same trunk mode if trunking
is used.
When trunking is used, all ports must be configured with the same
VLAN range. If it is not the same, packets will be dropped and the
ports will not form a channel when set to the auto or desirable mode.
All ports must be configured with the same speed and duplex settings.
If broadcast limits are configured on the ports, configure the limits for
all the ports or packets may be dropped.
The ports cannot be configured in a channel as dynamic VLAN ports.
Port security must be disabled on channeled ports.
All ports must be enabled in the channel. If you disable a port, a link
failure occurs.
Configuring EtherChannel
To create an EtherChannel bundle, use the set port channel command.
You must first make sure that all the conditions for EtherChannel have
been met.
Notice the switch output when we try to configure the ports on our 5000
switch as a bundle to the 1900 switch:
Todd5000> (enable) set port channel 1/1-2 on
Mismatch in trunk mode.
Mismatch in port duplex.
Mismatch in STP port priority.
Failed to set port(s) 1/1-2 channel mode to on.
Todd5000> (enable)
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