3com 5500-SI Manual De Usuario

C

HAPTER

 13: MSTP C

ONFIGURATION

Changes of port priorities can cause MSTP to redetermine the roles of ports, resulting 
in state transition of ports.

A lower port priority value indicates a higher port priority. If all ports of a switch have 
the same port priority setting, the actual port priorities are determined by the port 
indexes.

You can configure port priorities based on the specific networking requirements.

Configure the priority of port Ethernet1/0/1 in spanning tree instance 1 to be 16.

1 Configure in system view.

<S5500> system-view

System View: return to User View with Ctrl+Z.

[S5500] stp interface ethernet1/0/1 instance 1 port priority 16

2 Configure in Ethernet port view.

<S5500> system-view

System View: return to User View with Ctrl+Z.

[S5500] interface ethernet1/0/1

[S5500-Ethernet1/0/1] stp instance 1 port priority 16

Refer to “Configuring a Port to Connect to Point-to-Point Link”.

Refer to “Enabling MSTP”.

As mentioned previously, ports on an MSTP-enabled switch can operate in three 
modes: STP mode, RSTP mode, and MSTP mode. On a switched network, if a port on 
a switch running MSTP is connected to a switch running STP or RSTP, it automatically 
transits to STP or RSTP mode. But when the switch running STP or RSTP is 
disconnected, the port cannot transit back to MSTP mode automatically; it remains in 
STP or RSTP mode.

In this case, you can force the port to operate in MSTP mode by performing the 
mCheck operation.

Configure MSTP on the switch properly.

Table 165   Configure the priority of a port in Ethernet port view

Enter system view

system-view

-

Enter Ethernet port view

interface interface-type 
interface-number

-

Configure the port priority of 
the port

stp [ instance instance-id ] 
port priority priority

Required.

By default, all Ethernet ports of a 
switch have the same priority, 
namely 128.