Allied Telesis AT-S62 User Manual
Page 290
Chapter 20: Spanning Tree, Rapid Spanning Tree, and Multiple Spanning Tree Protocols
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Section IV: Spanning Tree Protocols
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 8 on page 277 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 13 lists the MSTP port cost with Auto Update
when a port is not part of a port trunk.
Table 14 lists the MSTP port costs with Auto Update when the port is
part of a port trunk.
Table 13. MSTP Auto Update Port Internal Path Costs
Port Speed
Port Cost
10 Mbps
2,000,000
100 Mbps
200,000
1000 Mbps
20,000
Table 14. MSTP Auto Update Port Trunk Internal Path Costs
Port Speed
Port Cost
10 Mbps
20,000
100 Mbps
20,000