3Com 7757 Configuration Manual page 249

Root Bridge/Secondary
Root Bridge
Configuration
n
MSTP can automatically choose a switch as a root bridge. You can also manually
specify the current switch as a root bridge by using the corresponding commands.
Root bridge configuration
Table 173 Specify the current switch as the root bridge of a specified spanning tree
Operation
Enter system view
Specify the current
switch as the root bridge
of a specified spanning
tree
Secondary root bridge configuration
Table 174 Specify the current switch as the secondary root bridge of a specified spanning
tree
Operation
Enter system view
Specify the current switch
as the secondary root
bridge of a specified
spanning tree
Using the stp root primary/stp root secondary command, you can specify a
switch as the root bridge or the secondary root bridge of the spanning tree
instance identified by the instance-id argument. If the value of the instance-id
argument is set to 0, the stp root primary/stp root secondary command specify
the current switch as the root bridge or the secondary root bridge of the CIST.
A switch can play different roles in different spanning tree instances. That is, it can
be the root bridges in a spanning tree instance and be a secondary root bridge in
another spanning tree instance at the same time. But in one spanning tree
instance, a switch cannot be the root bridge and the secondary root bridge
simultaneously.
When the root bridge fails or is turned off, the secondary root bridge becomes the
root bridge if no new root bridge is configured. If you configure multiple
secondary root bridges for a spanning tree instance, the one with the least MAC
address replaces the root bridge when the latter fails.
You can specify the network diameter and the Hello time parameters while
configuring a root bridge/secondary root bridge. Refer to "Network Diameter
Configuration" on page 252 and "MSTP Time-related Configuration" on page
252 for information about the network diameter parameter and the Hello time
parameter.
You can configure a switch as the root bridges of multiple spanning tree
■
instances. But you cannot configure two or more root bridges for one spanning
tree instance. So, do not configure root bridges for the same spanning tree
instance on two or more switches using the stp root primary command.
You can configure multiple secondary root bridges for one spanning tree
■
instance. That is, you can configure secondary root bridges for the same
Command
system-view
stp [ instance instance-id ] root primary
[ bridge-diameter bridgenumber
[ hello-time centi-seconds ] ]
Command
system-view
stp [ instance instance-id ] root
secondary [ bridge-diameter
bridgenumber [ hello-time
centi-seconds ] ]
Root Bridge Configuration
Description
-
Required
Description
-
Required
249