3Com Switch 7754, Configuration Manual

Page: 254 / 940

254 C
HAPTER
30: MSTP C
ONFIGURATION
As for the configuration of these three time-related parameters (that is, the Hello
time, Forward delay, and Max age parameters), the following formulas must be
met to prevent network jitter.
2 x (Forward delay - 1 second) >= Max age
Max age >= 2 x (Hello time + 1 second)
You are recommended to specify the network diameter of the switched network
and the Hello time by using the
stp root primary or stp root secondary
command. After that, the three proper time-related parameters are determined
automatically.
Configuration example
# Configure the Forward delay parameter to be 1,600 centiseconds, the Hello time
parameter to be 300 centiseconds, and the Max age parameter to be 2,100
centiseconds (assuming that the current switch operates as the CIST root bridge).
<SW7750> system-view
[SW7750] stp timer forward-delay 1600
[SW7750] stp timer hello 300
[SW7750] stp timer max-age 2100
Timeout Time Factor
Configuration
A switch regularly sends protocol packets to its neighboring devices at the interval
specified by the Hello time parameter to test the links. Normally, a switch regards
its upstream switch faulty if the former does not receive any protocol packets from
the latter in a period three times of the Hello time and then initiates the spanning
tree regeneration process.
Spanning trees may be regenerated even in a steady network if an upstream
switch continues to be busy. You can configure the timeout time factor to a larger
number to avoid this. Normally, the timeout time can be four or more times of the
Hello time. For a steady network, the timeout time can be five to seven times of
the Hello time.
Configuration procedure
Configuration example
# Configure the timeout time factor to be 6.
<SW7750> system-view
[SW7750] stp timer-factor 6
Maximum Transmitting
Speed Configuration
The maximum transmitting speed of a port specifies the maximum number of
configuration BPDUs a port can transmit in a period specified by the Hello time
Table 180 Configure timeout time factor
Operation Command Description
Enter system view system-view -
Configure the timeout time
factor for the switch stp timer-factor number Required
The timeout time
factor defaults to 3.