Configuring STP Bridge Parameters Configuring Spanning Tree Parameters
page 6-30 OmniSwitch AOS Release 7 Network Configuration Guide June 2013
If the switch is running in the per-VLAN Spanning Tree mode, then a forward delay time value is defined
for each VLAN instance. If the switch is running in the flat Spanning Tree mode, then the forward delay
time value is defined for the flat mode instance. In both cases, the default forward delay time is used.
Note. Specifying a low forward delay time can cause temporary network loops, because packets can get
forwarded before Spanning Tree configuration or change notices have reached all nodes in the network.
To change the bridge forward delay time value for a VLAN instance regardless of which mode (per-
VLAN or flat) is active for the switch, use the spantree forward-delay command with the vlan parame-
ter. For example, the following command changes the forward delay time for VLAN 455 to 10 seconds:
-> spantree vlan 455 forward-delay 10
To change the forward-delay time value for the flat mode CIST instance, use either the spantree forward-
delay command or the spantree forward-delay command with the cist parameter. Note that both
commands are available when the switch is running in either mode (per-VLAN or flat). For example, the
following commands change the forward-delay time value for the flat mode instance to 10:
-> spantree forward-delay 10
-> spantree cist forward-delay 10
Note. The forward delay time is not configurable for Multiple Spanning Tree Instances (MSTI). These
instances inherit the forward delay time from the flat mode instance (CIST).
Enabling/Disabling the VLAN BPDU Switching Status
BPDU are not switched on ports associated with VLANs that have Spanning Tree disabled. This can result
in a network loop if the VLAN has redundant paths to one or more other switches.
Allowing VLANs that have Spanning Tree disabled to forward BPDU to all ports in the VLAN, can help
to avoid this problem.
To enable or disable the switching of Spanning Tree BPDU for all VLAN and CIST instances when the
switch is running in the per-VLAN mode, use the spantree bpdu-switching command:
-> spantree bpdu-switching enable
-> spantree bpdu-switching disable
To enable or disable the switching of Spanning Tree BPDU for only the CIST instance when the switch is
running in the flat mode, use the spantree bpdu-switching command:
-> spantree cist bpdu-switching enable
-> spantree cist bpdu-switching disable
To enable or disable BPDU switching on a VLAN, use the vlan parameter along with spantree
bpdu-switching
command.For example, the following commands enable BPDU switching on VLAN 10
and disable it on VLAN 20:
-> spantree vlan 10 bpdu-switching enable
-> spantree vlan 20 bpdu-switching disable
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