stp timer forward-delay
Function
The stp timer forward-delay command sets the value of the Forward Delay of a switching device.
The undo stp timer forward-delay command restores the default value of the Forward Delay.
By default, the value of the Forward Delay of a switching device is 1500 centiseconds (15 seconds).
Format
stp [ vlan { vlan-id1 [ to vlan-id2 ] } &<1-10> ] timer forward-delay forward-delay
undo stp [ vlan { vlan-id1 [ to vlan-id2 ] } &<1-10> ] timer forward-delay
Parameters
| Parameter | Description | Value |
|---|---|---|
| vlan vlan-id1 [ to vlan-id2 ] | Specifies one or more VLANs in which the Forward Delay value is set.
In the stp timer forward-delay command, you can specify a maximum of 10 VLAN ranges. NOTE:
VLANs can be specified only when VBST is running. |
The value is an integer that ranges from 1 to 4094. |
| forward-delay | Specifies the value of the Forward Delay. | The value ranges from 400 to 3000 centiseconds by a step of 100. |
Views
System view or MSTP process view
Usage Guidelines
Usage Scenario
On a network running a spanning tree algorithm, if the network topology is changed, it takes time to advertise new BPDU configuration messages on the network. During this period, interfaces to be blocked may not be blocked in time and interface ever blocked may not be blocked. As a result, a temporary loop may be formed. To prevent this problem, you can use the Forward Delay timer to set a delay time. During the delay time, all interfaces are blocked temporarily.
The stp timer forward-delay command is used to set the Forward Delay timer.
Precautions
The value of the Forward Delay timer set on the root bridge is advertised to other devices of the same spanning tree using BPDUs. Then it becomes the value of the Forward Delay timer of all devices in the spanning tree.
2 x (Forward Delay - 1.0 second) ≥ Max Age
Max Age ≥ 2 x (Hello Time + 1.0 second)
Running the stp bridge-diameter command to set the network diameter is recommended. After the stp bridge-diameter command is run, the switching device sets optimum values for the three parameters, Hello Time, Forward Delay, and Max Age.
Example
# Set the Forward Delay to 2000 centiseconds (20 seconds) when STP/RSTP/MSTP is running.
<HUAWEI> system-view
[HUAWEI] stp timer forward-delay 2000
<HUAWEI> system-view
[HUAWEI] stp vlan 10 timer forward-delay 2000