3Com 3C13636 Configuration Manual page 367

3Com Router 3000 Ethernet Family
Configuration Guide
Restore the default priority of the bridge
port
The default priority of the bridge port is 128.
VI. Setting the Hello Time timer (optional)
A Hello Time timer is used to control the interval for sending BPDUs. Enabling STP on
a port starts a Hello Time timer. An appropriately set Hello Time timer allows the
bridge to discover link faults on the network without occupying many resources.
Perform the following configuration in system view.
Table 3-20 Set the Hello Time timer
Set the Hello Time timer
Restore default setting of the Hello
Time timer
By default, the time value for a Hello Time timer is 2 seconds.
When configuring a Hello Time timer, consider the following:
On a spanning tree, all bridges must use the Hello Time timer of the root bridge
instead of their own.
Set the Hello Time timer appropriately. A small Hello time timer may increase the
frequency of BPDU sending, increasing undesired CPU load. A large Hello Time
timer, on the contrary, may cause the bridge to take a frame loss for a link failure,
and then to recalculate the spanning tree. You are recommended to use the
default timer setting if possible.
VII. Setting the Forward Delay timer (optional)
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.
Perform the following configuration in system view.
Operation
Operation
3Com Corporation
3-18
Chapter 3 Bridge Configuration
Command
undo bridge-set bridge-set stp port
priority
Command
bridge stp timer hello seconds
undo bridge stp timer hello