Configuring Spanning Tree Timers

The following table describes the timers.

Table 1. Timers
Variable	Description
forward-time	Controls how fast a port changes its spanning tree state from Blocking state to Forwarding state.
hello-time	Determines how often the switch broadcasts its hello message to other switches. In case a bridge is root bridge for a topology then all bridges in that topology will use the value of hello time from the root bridge to broadcast their hello message.
max-age	The maximum time allowed for the Spanning Tree Protocol information learnt from the network on any port to be retained before it is discarded.

Execute the following commands to configure forward-time in the switch.
Type the following:
- Enter the Global Configuration Mode.
```
iS5comm# configure terminal
```
- Configure the spanning tree timer.
Note:
The forward-time range is 4-30. Default value is 15 seconds.
```
% PVRST is Started Enter Vlan Id For Configuration
```
```
iS5comm(config)# spanning-tree vlan 3 forward-time 5
```
Note:
If you get a message “Forward Time for the given instance is set”, then apply the no form of the forward-time command as shown below. The following relation should be observed.

2*(ForwardDelay -1)>=MaxAge >= 2*(Hello Time + 1),

then choose a new value for forward-time.
```
iS5comm(config)# spanning-tree vlan 2 forward-time 11
```
```
Forward Time for the given instance is set.
```
- Return to the Privileged EXEC Mode.
```
iS5comm(config)# exit
```
Execute the following commands to configure Hello Time.
Type the following:
- Enter the Global Configuration Mode.
```
iS5comm# configure terminal
```
- Configure hello-time.
Note:
The hello-time range is 1-2. Default value is 2 seconds.
```
iS5comm(config)# spanning-tree vlan 3 hello-time 2 
```
```
Hello Time for the given instance is set
```
- Return to the Privileged EXEC Mode.
```
iS5comm(config)# exit
```
Execute the following commands to configure Max Age.
Type the following:
- Enter the Global Configuration Mode.
```
iS5comm# configure terminal
```
- Configure max-age.
Note:
The max-age range is 6-40. Default value is 20 seconds.
```
iS5comm(config)# spanning-tree vlan 3 max-age 19 
```
```
Max Agefor the given instance is set
```
- Return to the Privileged EXEC Mode.
```
iS5comm(config)# exit
```

View the spanning tree information by executing the following show command.

Type the following:

iS5comm# show spanning-tree vlan 1

Hello Time 2 Sec, Max Age 19 Sec, Forward Delay 11 Sec

Spanning Tree Enabled Protocol PVRST

Bridge Id       Priority 32769

Address 00:01:02:03:04:01

Hello Time 2 sec, Max Age 19 sec, Forward Delay 11 sec

Name   Role         State        Cost     Prio   Type

----   ----         -----        ----     ----   -----

Gi0/1  Designated   Forwarding   200000   128    SharedLan

Gi0/2  Designated   Forwarding   200000   128    SharedLan

Note:

Execute the no form of the timer command (in Global Configuration mode) to set the spanning tree timers to their default values.

iS5comm(config-if)# no spanning-tree vlan <vlan-id> forward-time

iS5comm(config-if)# no spanning-tree vlan <vlan-id> hello-time

iS5comm(config-if)# no spanning-tree vlan <vlan-id> max-age

% PVRST is Started Enter Vlan Id For Configuration