You can configure
the device to become the MST root bridge.
command fails if the value required to be the root bridge is less than 4096. If
the software cannot lower the bridge priority any lower, the device returns the
Error: Failed to set root bridge for VLAN 1
It may be possible to make the bridge root by setting the priority
for some (or all) of these instances to zero.
The root bridge
for each MSTI should be a backbone or distribution device. Do not configure an
access device as the spanning tree primary root bridge.
diameter keyword, which is available only for MSTI 0
(or the IST), to specify the Layer 2 network diameter (that is, the maximum
number of Layer 2 hops between any two end stations in the Layer 2 network).
When you specify the network diameter, the device automatically sets an optimal
hello time, forward-delay time, and maximum-age time for a network of that
diameter, which can significantly reduce the convergence time. You can enter
hello keyword to override the automatically calculated
With the device
configured as the root bridge, do not manually configure the hello time,
forward-delay time, and maximum-age time using the
spanning-tree mst hello-time,
spanning-tree mst forward-time, and
spanning-tree mst max-age global configuration