3Com Switch 4500 26-Port Configuration Manual page 189

however, be careful and do not disable those involved. (The following
configuration takes GigabitEthernet 1/0/25 as an example.)
[4500]interface gigabitethernet 1/0/25
[4500-GigabitEthernet1/0/25]stp disable
c To configure Switch A as a root, you can either configure the Bridge priority of
it as 0 or simply use the command to specify it as the root.
Set the Bridge priority of Switch A to 0
[4500]stp priority 0
d Designate Switch A as the root, using the following command.
[4500]stp root primary
e Enable the Root protection function on every designated port.
[4500]interface Gigabitethernet 2/0/1
[4500-GigabitEthernet2/0/1]stp root-protection
[4500]interface Gigabitethernet 2/0/2
[4500-GigabitEthernet2/0/2]stp root-protection
2 Configure Switch B
a Enable RSTP globally.
[4500]stp enable
b The port RSTP defaults are enabled after global RSTP is enabled. You can
disable RSTP on those ports that are not involved in RSTP calculation, however,
be careful and do not disable those involved. (The following configuration
takes Ethernet 1/0/4 as an example.)
[4500]interface Ethernet 1/0/4
[4500-Ethernet1/0/4]stp disable
c Configure Switch C and Switch B to serve as standby of each other and sets
the Bridge priority of Switch B to 4096.
[4500]stp priority 4096
d Enable the Root protection function on every designated port.
[4500]interface Ethernet 1/0/1
[4500-Ethernet1/0/1]stp root-protection
[4500]interface Ethernet 1/0/2
[4500-Ethernet1/0/2]stp root-protection
[4500]interface Ethernet 1/0/3
[4500-Ethernet1/0/3]stp root-protection
RSTP operating mode, time parameters, and port parameters take default
values.
3 Configure Switch C
a Enable RSTP globally.
[4500]stp enable
b The port RSTP defaults are enabled after global RSTP is enabled. You can
disable RSTP on those ports that are not involved in RSTP calculation, however,
be careful and do not disable those involved. (The following configuration
takes Ethernet 1/0/4 as an example.)
[4500]interface Ethernet 1/0/4
[4500-Ethernet1/0/4]stp disable
RSTP Configuration Example 187