Adjusting Bridge Protocol Data Unit (BPDU) Intervals

Adjusting the Bridge Hello Time

Caution

Caution: Poorly chosen adjustments to bridge and port hello time parameters can have a negative impact on network performance. It is recommended that you do not change these parameters unless you are familiar with Spanning Tree configuration and have determined that adjustments are necessary. Please refer to the IEEE 802.1D specification for guidance.

Hello time is the interval, in seconds, at which the bridge or individual ports send BPDU messages. By default, bridge hello mode is enabled, meaning the device uses a single bridge administrative hello time.

Adjust the bridge hello time as follows:

1. Check the status of bridge hello mode:

   show spantree bridgehellomode

2. If necessary, re-enable bridge hello mode:

   set spantree bridgehellomode enable

3. Set a new hello time interval:

   set spantree hello interval

   Valid interval values are 1–10.

Adjusting Port Hello Times

You can set the device to use per-port administrative hello times by disabling bridge hello mode and adjusting the hello time interval for one or more ports as follows:

1. Check the status of bridge hello mode:

   show spantree bridgehellomode

2. If necessary, disable bridge hello mode:

   set spantree bridgehellomode disable

3. Set a new hello time interval for one or more ports:

   set spantree porthello port-string interval

   Valid interval values are 10–100

Adjusting the Forward Delay Interval

When rapid transitioning is not possible, forward delay is used to synchronize BPDU forwarding. The forward delay interval is the amount of time spent listening for topology change information after an interface has been activated for bridging and before forwarding actually begins. This delay is required because every device must receive information about topology changes before it starts to forward frames. In addition, each port needs time to listen for conflicting information that would make it return to a blocking state. Otherwise, temporary data loops might result.

Use this command to adjust the forward delay interval setting:

set spantree fwddelay delay

Valid delay values are 4–30.

Defining the Maximum Age Time

If a bridge does not hear BPDUs from the root bridge within the interval (number of seconds) specified as maximum age time, it assumes that the network has changed and recomputes the Spanning Tree topology. By adjusting this value, you can configure support for a maximum diameter from the STP root of up to 40 bridges. By default, Extreme Networks switching devices are set with a maximum age time of 20 seconds, supporting a 20-bridge span from the root bridge.

Use this command to adjust the maximum age setting:

set spantree maxage agingtime

Valid agingtime values are 6–40 (seconds).