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Bridge Spanning Tree 3-21
NB-30 Bridging
Bridge Port Level Parameters
The following Þelds are applicable to each bridge port on the NB-30.
Priority
If two or more ports on the same bridge are connected to the same LAN segment,
they will receive the same Root ID/Root Cost/Bridge ID information in
ConÞguration BPDUs received at each port. In this case, the BPDUÕs Port ID
information Ñ the transmitting portÕs identiÞer and its manageable Priority
component Ñ is used to determine which is the Designated Port for that segment.
A lower assigned value gives the port a higher Priority when BPDUs are
compared. The allowable range is 0-FF hexadecimal (0-255 decimal); the default is
80 hexadecimal.
Path Cost
Displays the cost that this port will contribute to the calculation of the overall
Root path cost in a ConÞguration BPDU transmitted by this bridge port. You can
lower a portÕs Path Cost to make the port more competitive in the selection of the
Designated Port Ñ for example, you may want to assign a lower path cost to a
port on a higher performance bridge. The allowable range is 1 to 65535.
Designated Cost
Displays the cost of the path to the Root Bridge of the Designated Port on the
LAN to which this port is attached. This cost is added to the Path Cost to test the
value of the Root Path Cost parameter received in ConÞguration BPDUs.
Designated Root
Displays the unique bridge identiÞer of the bridge that is assumed to be the Root
Bridge.
Designated Bridge
Displays the network address portion of the Bridge ID (MAC address/priority
component) for the bridge that is believed to be the Designated Bridge for the
LAN associated with this port.
The Designated Bridge ID, along with the Designated Port and Port IdentiÞer
parameters for the port, is used to determine whether this port should be the
Designated Port for the LAN to which it is attached. The Designated Bridge ID is
also used to test the value of the Bridge IdentiÞer parameter in received BPDUs.
Designated Port
Displays the network address portion of the Port ID (which includes a
manageable priority component) of the port believed to be the Designated Port
for the LAN associated with this port.
The Designated Port ID, along with the Designated Bridge and Port IdentiÞer
parameters for the port, is used to determine whether this port should be the
Designated Port for the LAN to which it is attached. Management also uses it to
determine the Bridged LAN topology.