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Configuring STP Bridge Parameters
To change the bridge priority value for a VLAN instance regardless of which mode (per-VLAN or flat) is
active for the switch, use the
following command changes the priority for VLAN 455 to 25590:
-> spantree vlan 455 priority 25590
Note. If PVST+ mode is enabled on the switch, then the priority values can be assigned only in the multi-
ples of 4096 to be compatible with the Cisco MAC Reduction mode; any other values result in an error
message.
To change the bridge priority value for the flat mode CIST instance, use either the
command or the
spantree priority
able when the switch is running in either mode (per-VLAN or flat). For example, the following commands
change the bridge priority value for the flat mode instance to 12288:
-> spantree cist priority 12288
-> spantree priority 12288
The bridge priority value is also configurable for a Multiple Spanning Tree Instance (MSTI). To
configure this value for an MSTI, use the
ify a priority value that is a multiple of 4096. For example, the following command configures the priority
value for MSTI 10 to 61440:
-> spantree msti 10 priority 61440
Configuring the Bridge Hello Time
The bridge hello time interval is the number of seconds a bridge waits between transmissions of
Configuration BPDU. When a bridge is attempting to become the root or if it has become the root or a
designated bridge, it sends Configuration BPDU out all forwarding ports once every hello time value.
The hello time propagated in a root bridge Configuration BPDU is the value used by all other bridges in
the tree for their own hello time. Therefore, if this value is changed for the root bridge, all other bridges
associated with the same STP instance adopt this value as well.
Note. Lowering the hello time interval improves the robustness of the Spanning Tree algorithm.
Increasing the hello time interval lowers the overhead of Spanning Tree processing.
If the switch is running in the per-VLAN Spanning Tree mode, then a hello time value is defined for each
VLAN instance. If the switch is running in the flat Spanning Tree mode, then a hello time value is defined
for the single flat mode instance. In both cases, the default hello time value is used.
To change the bridge hello time value for a VLAN instance regardless of which mode (per-VLAN or flat)
is active for the switch, use the
following command changes the hello time for VLAN 455 to 5 seconds:
-> spantree vlan 455 hello-time 5
To change the bridge hello time value for the flat mode CIST instance, use either the
command or the
spantree hello-time
available when the switch is running in either mode (per-VLAN or flat). For example, the following
commands change the hello time value for the flat mode instance to 10:
page 5-28
spantree priority
command with the vlan parameter. For example, the
command with the cist parameter. Note that both commands are avail-
spantree priority
spantree hello-time
command with the vlan parameter. For example, the
command with the cist parameter. Note that both commands are
OmniSwitch AOS Release 7 Network Configuration Guide
Configuring Spanning Tree Parameters
spantree priority
command with the msti parameter and spec-
spantree hello-time
March 2011
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