Allied Telesis AT-S62 - Manual (Page 265)

AT-S62 Web Browser Interface User’s Guide
Section IV: Spanning Tree Protocols 265
An MSTI-specific parameter can be set on a per MSTI basis. This
means that you can assign different values to a port’s MSTI-
specific parameters for each spanning tree instance where the
port is a member. These parameters are:
❑ Internal path cost
❑ Port priority
When setting an MSTI-specific parameter, use the MSTI List in the
window to select the intended MSTI. It should be noted that the
MSTI List shows all of the spanning tree instances on the switch,
and not just those where the selected port is currently a member.
If you select an MSTI where the port is not a member, you can pre-
configure the parameter in the event you later add the port as a
member of the MSTI through a VLAN assignment.
Port Priority
This parameter is used as a tie breaker when two or more ports are
determined to have equal costs to the regional root bridge. The
range is 0 to 240 in increments of 16. To select a port priority for a
port, you enter the increment of the desired value. Table 7 on
page 252 lists the values and increments. The default value is 128,
which is increment 8.
This is an MSTI-specific parameter. If the port you are configuring
is a member of more than one MSTI, you can assign the port a
different priority value for each of its MSTI memberships. This is
accomplished by entering a new priority value and then using the
MSTI List option to select the MSTIs where you want the new
parameter setting for the port to be applied.
Port Internal Path Cost
The port cost of the port if the port is connected to a bridge which
is part of the same MSTP region. The range is 0 to 200,000,000. The
default setting is Auto-detect, which sets port cost depending on
the speed of the port. Table 10 lists the MSTP port cost with Auto
Update when a port is not part of a port trunk.
Table 12 MSTP Auto Update Port Internal Path Costs
Port Speed Port Cost
10 Mbps 2,000,000
100 Mbps 200,000
1000 Mbps 20,000