Intel IXM5414E manual Creating a stable topology, 258, Variable Description Default value

Table 10. STP parameters – bridge

Parameter	Description	Default value
Bridge hello time	The length of time between broadcasts of the hello	2 seconds
	message.
Bridge maxage time	The length of time before topology information or	20 seconds
	information from BPDUs is discarded because it has
	aged out.
Bridge forward delay	The amount of time spent by a port in the discarding	15 seconds
time	states waiting for a BPDU that might return the port to
	the discarding state if the bridge is in IEEE 802.1D
	compatibility mode or if operPointToPointMAC and
	operEdgePort are both False.

The following table shows the user-configurable STP parameters for the ports on the bridge.

Table 11. STP port parameters

Variable	Description	Default value
Port priority	The relative priority for each port. The lower the number	128
	the higher the priority and the greater the likelihood of
	the port being elected as the root port.
Port path cost	A value used by STP to evaluate paths.	auto (calculated based
		on the link speed)

Creating a stable topology

For STP to arrive at a stable network topology, the following information is used:

•A unique identifier for each bridge

•An identifier for each bridge port

•The path cost to the root bridge associated with each bridge port

STP communicates between bridges on the network using bridge protocol data units (BPDUs). There are two types of BPDUs:

•Configuration messages containing a spanning tree priority vector describing the transmitter’s view of the spanning tree topology

•Topology Change Notification (TCN) messages

Each BPDU includes the following information:

•The unique identifier of the bridge that the transmitting bridge currently recognizes as the root bridge

•The path cost to the root from the transmitting port

•The port identifier of the transmitting port

258 Intel® Blade Server Ethernet Switch Module IXM5414E