Command Reference Guide

3Com Router 3000 Ethernet Family
Command Reference Guide Chapter 3 Bridge Configuration Commands
3Com Corporation
3-9
Use the undo bridge stp timer forward-delay command to restore the default.
A link fault on the network may cause a spanning-tree recalculation immediately;
however, it takes time for the new BPDU to propagate throughout the entire network. If
new root ports and designated ports start forwarding frames immediately after they are
elected, a temporary loop may occur.
To resolve the problem, STP adopts a state transition mechanism, where a root or
designated port must undergo a transitional state before it enters the forwarding state
to forward frames. The duration of this transitional state depends on the setting of a
timer called Forward Delay timer. It ensures that the new BPDU has been propagated
throughout the network before frames are forwarded according to the latest topology.
When configuring a Forward Delay timer, consider the following:
z On a spanning tree, all bridges must use the Forward Delay timer of the root
bridge instead of their own.
z Use the default Forward Delay timer setting if possible. A small forward delay may
create temporary path redundancy; while a large forward delay may increase the
time required for the topology of the spanning tree to converge. In the latter case,
network connectivity recovery may take a long time.
Example
# Set the Forward Delay timer on the bridge to 50 seconds.
[Router] bridge stp timer forward-delay 50
3.1.13 bridge stp timer hello
Syntax
bridge stp timer hello seconds
undo bridge stp timer hello
View
System view
Parameter
seconds: Value for the Hello Time timer on the bridge, in the range 1 to 10 seconds.
The default value is 2 seconds.
Description
Use the bridge stp timer hello command to set the Hello Time timer on the bridge.
Use the undo bridge stp timer hello command to restore the default.