Reference Guide

Multiple Spanning Tree Protocol (MSTP) | 549
View the current values for MSTP parameters using the show running-config spanning-tree mstp command
from EXEC privilege mode.
Figure 25-7. Viewing the Current Values for MSTP Parameters
Modify Interface Parameters
You can adjust two interface parameters to increase or decrease the probability that a port becomes a
forwarding port:
• Port cost is a value that is based on the interface type. The greater the port cost, the less likely the port
will be selected to be a forwarding port.
• Port priority influences the likelihood that a port will be selected to be a forwarding port in case that
several ports have the same port cost.
Table 25-2 lists the default values for port cost by interface.
Change the hello-time parameter.
Note: With large configurations (especially those with more ports) Dell
Force10 recommends that you increase the hello-time.
Range: 1 to 10
Default: 2 seconds
hello-time seconds PROTOCOL MSTP
Change the max-age parameter.
Range: 6 to 40
Default: 20 seconds
max-age seconds PROTOCOL MSTP
Change the max-hops parameter.
Range: 1 to 40
Default: 20
max-hops number PROTOCOL MSTP
Table 25-2. MSTP Default Port Cost Values
Port Cost Default Value
100-Mb/s Ethernet interfaces 200000
1-Gigabit Ethernet interfaces 20000
Task Command Syntax Command Mode
FTOS(conf-mstp)#forward-delay 16
FTOS(conf-mstp)#exit
FTOS(conf)#do show running-config spanning-tree mstp
!
protocol spanning-tree mstp
no disable
name my-mstp-region
MSTI 1 VLAN 100
MSTI 2 VLAN 200-300
forward-delay 16
MSTI 2 bridge-priority 4096
FTOS(conf)#