Configuring Port Priority - Alcatel OmniSwitch 6600 Family Network Configuration Manual

Configuring Spanning Tree Port Parameters
To enable or disable the Spanning Tree status for a link aggregate, use the bridge slot/port commands
described above but specify a link aggregate control number instead of a slot and port. For example, the
following command disables Spanning Tree for link aggregate 10 associated with VLAN 755:
-> bridge 755 10 disable
For more information about configuring an aggregate of ports, see
Aggregation," and Chapter 13, "Configuring Dynamic Link Aggregation."

Configuring Port Priority

A bridge port is identified within the Spanning Tree by its Port ID (a 16-bit or 32-bit hex number). The
first 4 bits of the Port ID contain a priority value and the remaining 12 bits contain the physical switch port
number. The port priority is used to determine which port offers the best path to the root when multiple
paths have the same path cost. The port with the highest priority (lowest numerical priority value) is
selected and the others are put into a blocking state. If the priority values are the same for all ports in the
path, then the port with the lowest physical switch port number is selected.
By default, Spanning Tree is enabled on a port and the port priority value is set to 7. If the switch is
running in the 1x1 Spanning Tree mode, then the port priority applies to the specified VLAN instance
associated with the port. If the switch is running in the flat Spanning Tree mode, then the port priority
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 multiple VLANs.
To change the port priority value for a VLAN instance, specify a VLAN ID with the
priority command when the switch is running in the 1x1 mode. For example, the following command sets
the priority value for port 8/1 to 3 for the VLAN 10 instance:
-> bridge 10 8/1 priority 3
The explicit bridge cist slot/port priority
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 priority 3
To change the port priority value for the flat mode instance, use either the
command or the bridge cist slot/port priority
the switch is running in either mode (1x1 or flat) and an instance number is not required. For example, the
following commands change the priority value for port 1/24 for the flat mode instance to 15:
-> bridge 1/24 priority 15
-> bridge cist 1/24 priority 10
As in previous releases, it is possible to configure the flat mode instance with the bridge slot/port prior-
ity command by specifying 1 as the instance number (e.g., bridge 1 1/24 priority 15). 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 priority value is also configurable for an 802.1s Multiple Spanning Tree Instance (MSTI). To
configure this value for an MSTI, use the explicit
MSTI ID for the instance number. For example, the following command configures the priority value for
port 1/12 for MSTI 10 to 5:
-> bridge msti 10 1/12 priority 5
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
page 5-22
command configures the port priority value for a VLAN
command. Note that both commands are available when
bridge msti slot/port priority
OmniSwitch 6600 Family Network Configuration Guide
Configuring Spanning Tree Parameters
Chapter 12, "Configuring Static Link
bridge slot/port
bridge slot/port priority
command and specify the
April 2006