Cabletron Systems CSX400, CSX200 Spanning Tree Mode, 4-62, Bridging, Source Route Configuration

Bridging

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 radio 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 radio 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 (discussed in
	earlier in this chapter).
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).

-Disabled (not participating in the bridging process or in operation of the Spanning Tree Algorithm and protocol). If the Spanning Tree Mode is set to Disabled, the bridge port will not send or accept any STE frames. Any STE frame received will be discarded. The Spanning Tree Expl Þeld at the ConÞguration window, and the STE Frames Þeld at the Status window will both read ÒDisabled.Ó

4-62 Source Route Configuration