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DWS-1008 User’s Manual
D-Link Systems, Inc.
Configuring and Managing STP
212
D-Link Systems, Inc.
Bridge Priority
The bridge priority determines the switch’s eligibility to become the root bridge. You can set
this parameter globally or on individual VLANs.
The root bridge is elected based on the bridge priority of each device in the spanning tree.
The device with the highest bridge priority is elected to be the root bridge for the spanning
tree. The bridge priority is a numeric value from 0 through 65,535. Lower numeric values
represent higher priorities. The highest priority is 0, and the lowest priority is 65,535. The
default bridge priority for all devices is 32,768.
If more than one device has the highest bridge priority (lowest numeric value), the device with
the lowest MAC address becomes the root bridge. If the root bridge fails, STP elects a new
root bridge based on the bridge priorities of the remaining bridges.
Port Cost
Port cost is a numeric value that STP adds to the total cost of a path to the root bridge.
When a designated bridge has multiple equal-cost paths to the root bridge, the designated
bridge uses the path with the lowest total cost. You can set this parameter on an individual
port basis, for all VLANs the port is in, or for specific VLANs.
You can specify a value from 1 through 65,535 for the port cost. The default depends on the
port speed and link type. Table 21 lists the defaults for STP port path cost.
SNMP Port Path Cost Defaults
Port Speed
Link Type
Default Port Path
Cost
100 Mbps
Full Duplex Aggregate
Link (Port Group)
19
100 Mbps
Full Duplex
18
100 Mbps
Half Duplex
19
10 Mbps
Full Duplex Aggregate
Link (Port Group)
19
10 Mbps
Full Duplex
95
10 Mbps
Half Duplex
100
Port Priority
Port priority is the eligibility of the port to be the designated port to the root bridge, and
thus part of the path to the root bridge. When the switch has more than one link to the root
bridge, STP uses the link with the lowest priority value. You can set this parameter on an
individual port basis, for all VLANs the port is in, or for specific VLANs.
Specify a priority from 0 (highest priority) through 255 (lowest priority). The default is 128.