Command Line Interface Reference Guide > The Information Menu > /info/l2 Layer 2 Information Menu > /info/l2/stg Layer 2 Spanning Tree Group Information
/info/l2/stg
Layer 2 Spanning Tree Group Information
When multiple paths exist on a network, Spanning Tree Protocol (STP) configures the network so that Alteon uses only the most efficient path.
Note: Alteon supports up to 16 multiple Spanning Trees or Spanning Tree Groups.
 
Spanning Tree Group 1: On (STP/PVST)
VLANs: 1 10 20 100 220

Current Root: Path-Cost Port Hello MaxAge FwdDel Aging
8000 00:03:b2:52:21:00 5 2 2 20 15 300

Parameters: Priority Hello MaxAge FwdDel Aging
32768 2 20 15 300

Port Priority Cost State Designated Bridge Des Port
------ -------- ---- ---------- ---------------------- --------
1 128 1! BLOCKING 8064-00:19:aa:cb:71:80 800b
2 128 5! FORWARDING 8000-00:03:b2:52:21:00 8002
3 128 0! DISABLED
4 128 0! DISABLED
5 128 0! DISABLED
6 128 0! DISABLED
7 128 0! DISABLED
8 128 0! DISABLED
9 128 0! DISABLED
10 128 0! DISABLED
11 128 0! DISABLED
12 128 0! DISABLED
13 128 0! DISABLED
14 128 0! DISABLED
15 128 0! DISABLED
16 128 0! DISABLED
! = Automatic path cost.

Number of topology changes - 179
Time since last topology change - 26 days 23 hours 9 minutes 18 seconds
Alteon uses the IEEE 802.1d Spanning Tree Protocol (STP). In addition to seeing if STP is enabled or disabled, you can view the following STP bridge information:
*Priority
*Hello interval
*Maximum age value
*Forwarding delay
*Aging time
*Number of topology changes per STG
*Topology change time per STG
You can also see the following port-specific STP information:
*Port number and priority
*Cost
*State
*Designated Bridge
*Designated Port
The following table describes the STP parameters:
 
Spanning Tree Parameter Descriptions 
Parameter
Description
Priority (bridge)
Controls which bridge on the network becomes the STP root bridge.
Hello
Specifies, in seconds, how often the root bridge transmits a configuration bridge protocol data unit (BPDU). Any bridge that is not the root bridge uses the root bridge hello value.
MaxAge
Specifies, in seconds, the maximum time the bridge waits without receiving a configuration bridge protocol data unit before it re-configures the STP network.
FwdDel
Specifies, in seconds, the time that a bridge port has to wait before it changes from learning state to forwarding state.
Aging
Specifies, in seconds, the time the bridge waits without receiving a packet from a station before removing the station from the forwarding database.
priority (port)
Helps determine which bridge port becomes the designated port. In a network topology that has multiple bridge ports connected to a single segment, the port with the lowest port priority becomes the designated port for the segment.
Cost
Helps determine the designated port for a segment. As a rule, the faster the port, the lower the path cost. A setting of 0 indicates that the cost is set to the appropriate default after the link speed has been auto negotiated.
State
The state field shows the current state of the port.
Values:
*BLOCKING
*LISTENING
*LEARNING
*FORWARDING
*DISABLED
Designated Bridge
The designated bridge resides closest to the root bridge and is responsible for forwarding packets from LAN towards the root bridge. This bridge displays as a character string starting with the bridge priority (1 through 65535) followed by a hyphen and six-byte Alteon MAC address.
Designated port
Identifies a physical port. This is a number that is the numerical sum of the bridge priority and the actual physical port number. For example, a physical port number 4 with bridge priority 32768 displays as 32678+4=32772.