Configuring the Root

Configuring the Root
After you choose the best switch to become your root bridge, you can use the Cisco commandline
interface (CLI) to configure the STP parameters in a switched network.
Scaling the Spanning Tree Protocol
507
The command to configure the STP is
set
spantree
. The following switch output (from our Catalyst
4000) shows the different command parameters you can use when configuring the STP. We are
interested in the
set
spantree
root
and
set
spantree
root
secondary
commands at this point:
Terry_4000(enable)
set spantree ?
Set spantree commands:
----------------------------------------------------------------------------
set spantree disable Disable spanning tree
set spantree enable Enable spanning tree
set spantree fwddelay Set spantree forward delay
set spantree hello Set spantree hello interval
set spantree help Show this message
set spantree maxage Set spantree max aging time
set spantree portcost Set spantree port cost
set spantree portfast Set spantree port fast start
set spantree portpri Set spantree port priority
set spantree portvlancost Set spantree port cost per vlan
set spantree portvlanpri Set spantree port vlan priority
set spantree priority Set spantree priority
set spantree root Set switch as primary or secondary root
set spantree uplinkfast Enable or disable uplinkfast groups
set spantree backbonefast Enable or disable fast convergence
Terry_4000 (enable)
The set spantree root command sets the primary root bridge for a specific VLAN, or even
for all your VLANs. The set spantree root secondary command enables you to configure
a backup root bridge.
In the following switch output, notice the options that are available with the set spantree
root command:
Terry_4000> (enable) set spantree root ?
Usage: set spantree root [secondary] <vlans> [dia <network_diameter>]
[hello <hello_time>]
(vlans = 1..1005, network_diameter = 2..7, hello_time = 1..10)
Table 16.1 shows the parameters available with the set spantree command and their
definitions.