Configuring Stp Port Parameters; Enabling/Disabling Stp On A Port; Stp On Link Aggregate Ports - Alcatel OmniSwitch 6624 Network Configuration Manual

Configuring STP Port Parameters

Configuring STP Port Parameters
The following sections provide information and procedures for using CLI commands to configure STP
port parameters. These parameters determine the behavior of a port for a specific VLAN Spanning Tree
instance (1x1 STP mode) or for a single Spanning Tree instance applied to the entire switch (flat STP
mode).
When a switch is running in the 1x1 STP mode, each VLAN is in essence a virtual STP bridge with its
own STP instance and configurable parameters. To change STP port parameters while running in this
mode, a VLAN ID is specified to identify the VLAN STP instance associated with the specified port.
When a switch is running in the flat Spanning Tree mode, VLAN 1 is specified for the VLAN ID. It is
possible to configure STP parameters on other VLANs while running in this mode, but only VLAN 1
parameter values apply to all Spanning Tree ports.
Only bridged ports participate in the Spanning Tree Algorithm. A port is considered bridged if it meets all
the following criteria:
Port is either a fixed (non-mobile) port, an 802.1Q tagged port or a link aggregate logical port.
•
Spanning tree is enabled on the port.
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Port is assigned to a VLAN that has Spanning Tree enabled.
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Port state (forwarding or blocking) is dynamically determined by the Spanning Tree Algorithm, not
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manually set.

Enabling/Disabling STP on a Port

By default, STP is enabled on all ports. If STP is disabled on a port, the port is put in a forwarding state for
the Spanning Tree instance. For example, if a port is associated with both VLAN 10 and VLAN 20 and
STP is disabled on the port for VLAN 20, the port state is set to forwarding for VLAN 20. However, the
VLAN 10 STP instance still controls the port's state as it relates to VLAN 10. This example assumes the
switch is running in the 1x1 Spanning Tree mode.
If the switch is running in the flat Spanning Tree mode, then disabling the port STP status applies across
all VLANs associated with the port. VLAN 1 is referenced as the port's VLAN, even if the port is associ-
ated with other VLANs.
To enable or disable the STP status on a port, enter bridge followed by an existing VLAN ID (or VLAN 1
if using a flat Spanning Tree instance) then the port's slot/port designation followed by enable or disable.
For example, the following commands enable STP on port 1 on slot 8 for VLAN 10 and disable STP on
port 2 on slot 6 for VLAN 20:
-> bridge 10 8/1 enable
-> bridge 20 6/2 disable

STP on Link Aggregate Ports

Physical ports that belong to a link aggregate do not participate in the Spanning Tree Algorithm. Instead,
the algorithm is applied to the aggregate logical link (virtual port) that represents a collection of physical
ports. To enable or disable the STP status for a link aggregate, use the same bridge command, but specify
a link aggregate control number instead of a slot and port. For example, the following command disables
STP for link aggregate 29 associated with VLAN 755:
-> bridge 755 29 disable
page 5-14 OmniSwitch 6624/6648 Network Configuration Guide
Configuring Spanning Tree Parameters
April 2004