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Configuring Spanning Tree Port Parameters Configuring Spanning Tree Parameters
page 5-24 OmniSwitch 6600 Family Network Configuration Guide April 2006
By default, Spanning Tree is enabled on a port and the path cost is set to zero. If the switch is running in
the 1x1 Spanning Tree mode, then the port path cost applies to the specified VLAN instance associated
with the port. If the switch is running in the flat Spanning Tree mode, then the port path cost applies across
all VLANs associated with the port. The flat mode instance is specified as the port’s instance, even if the
port is associated with other VLANs.
To change the port path cost value for a VLAN instance, specify a VLAN ID with the bridge slot/port
path cost command when the switch is running in the 1x1 mode. For example, the following command
configures a 16-bit path cost value for port 8/1 for VLAN 10 to 19 (the port speed is 100 MB, 19 is the
recommended value).
-> bridge 10 8/1 path cost 19
The explicit bridge 1x1 slot/port path cost command configures the port path cost value for a VLAN
instance when the switch is running in either mode (1x1 or flat). For example, the following command
performs the same function as the command in the previous example:
-> bridge 1x1 10 8/1 path cost 19
To change the port path cost value for the flat mode instance, use either the bridge slot/port path cost
command or the bridge cist slot/port path cost command. Note that both commands are available when
the switch is running in either mode (1x1 or flat) and an instance number is not required. For example, the
following commands configure a 32-bit path cost value for port 1/24 for the flat mode instance to 20,000
(the port speed is 1 GB, 20,000 is the recommended value):
-> bridge 1/24 path cost 20000
-> bridge cist 1/24 path cost 20000
As in previous releases, it is possible to configure the flat mode instance with the bridge slot/port path
cost command by specifying 1 as the instance number (e.g., bridge 1 1/24 path cost 19). However, this is
only available when the switch is already running in the flat mode and STP or RSTP is the active protocol.
The port path cost value is also configurable for an 802.1s Multiple Spanning Tree Instance (MSTI). To
configure this value for an MSTI, use the explicit bridge msti slot/port path cost command and specify
the MSTI ID for the instance number. For example, the following command configures the path cost value
for port 1/12 for MSTI 10 to 19:
-> bridge msti 10 1/12 path cost 19
Note that when MSTP (802.1s) is the active flat mode protocol, explicit Spanning Tree bridge commands
are required to configure parameter values. Implicit commands are for configuring parameters when the
STP or RSTP protocols are in use. See Chapter 6, “Using 802.1s Multiple Spanning Tree,” for more infor-
mation.
1 Gbps 4
10 Gbps 2
Link Speed
IEEE 802.1D
Recommended Value