Network Router User Manual

Source Route Configuration 2-61
Bridging
Bridge Number
The Bridge Number uniquely identiÞes a bridge port when more than one bridge
is used to span the same two segments. The Bridge Number should be in the
range of 0 to 15.
You can use the Set button at the bottom of the window to change the bridge
number of the port, as explained in Making and Setting Changes, page 2-62.
Current source routing protocols allow a range of 0 to 15 (0ÐF hexadecimal) for
the bridge number identiÞer. If no bridge number is assigned to the device, a
default value of 1 will appear in this Þeld.
Spanning Tree Mode
Indicates how a port on the device will behave with an incoming single-route
broadcast (Spanning Tree ExplorerÑSTE) frame. You can conÞgure this Þeld with
the option buttons and checkboxes, or via the MIBTools utility or local
management.
This Þeld allows you to conÞgure a Spanning Tree for your network. You can set
the Spanning Tree Mode to Auto or Manual using the option buttons. We
recommend that all bridges in your network topology have the same setting for
Spanning Tree Mode (i.e., all set to Auto or all set to Manual).
Auto If the Spanning Tree Mode is set to Auto, a port that implements
the Spanning Tree Algorithm (STA) and is enabled and in the
forwarding state will accept and relay STE frames onto its
attached segment.
Using STA, a bridge port will only forward frames if it is the
designated port for its attached segment. A port is ÒdesignatedÓ
for its segment if it has the lowest Root Path Cost of all bridge
ports attached to that segment. The Root Path Cost is the lowest
total path cost calculated by adding the costs of each port along
the path of a frame that traverses the bridge topology from the
root to that port (including its own path cost).
If two ports on a segment have equal Root Path Costs, the port on
the bridge with the highest priority bridge identiÞer (for
convenience sake, that have the lowest numerical value) will be
chosen as the root port.
You can affect Spanning Tree topology by changing the deviceÕs
bridge priority (Bridge Label) and path cost for its port pair (path
cost increment) via the Spanning Tree window, page 2-34.
Manual If the Spanning Tree Mode is set to Manual, you can manually
conÞgure the bridge to forward STE frames (i.e., manually
establish a Spanning Tree for STE frames by determining which
bridge in a parallel series of bridges will forward these frames).
If you set the Spanning Tree Mode to Manual, you can use the Enable or Disable
checkboxes to set a portÕs Spanning Tree Enable State to:
¥ Enabled (participating in frame relay).