Ascii-File-Only Syntax; Selecting The Vlan Bridge Protocol (802.1D Or 802.1W) - Alcatel OmniSwitch 6800 Series Network Configuration Manual

Configuring Spanning Tree Parameters

ASCII-File-Only Syntax

When Spanning Tree parameters are configured and then saved in an ASCII file (typically through the
configuration snapshot command), the commands included in the file will contain syntax indicating the
common Spanning Tree instance and/or operating mode to which the command applies. For example:
!========================================!
! File: asc.4.snap
!========================================!
! Spanning tree :
bridge mode 1x1
bridge msti 0
bridge 1x1 3 max age 15
bridge 1x1 4 hello time 5
bridge 1x1 5 priority 16384
In the above example ASCII file, the 1x1 keywords were added to the syntax of three of the commands:
bridge max age, bridge hello time, and bridge priority. The parameter values specified by these
commands will apply when the switch is operating in the 1x1 Spanning Tree mode. If these same
commands were intended for the flat Spanning Tree mode, the cist keyword would appear in the syntax.
The cist and msti keywords designate the Spanning Tree instance 0, which is the flat Spanning Tree mode
instance. At this time, instance 0 is the only instance in the flat mode that is supported.
Note that using these keywords on the command line is not supported in this release. However, 1x1 is a
supported parameter value in the bridge mode 1x1 command.

Selecting the VLAN Bridge Protocol (802.1D or 802.1w)

The switch supports two Spanning Tree Algorithms: 802.1D (standard) and 802.1w (rapid reconfigura-
tion). If the switch is running in the 1x1 Spanning Tree mode, then a protocol is selected for each VLAN.
When a VLAN is created, STP is enabled and 802.1D is selected by default. If the switch is running in the
flat Spanning Tree mode, then the protocol is selected for instance 0, but applies across all VLANs config-
ured on the switch.
The 802.1w standard is an amendment to the 802.1D document and describes the rapid Spanning Tree
Algorithm and Protocol (RSTP). The RSTP provides rapid reconfiguration by allowing blocked ports to
transition directly into a forwarding state, bypassing the listening and learning states.
Although it supports the 802.1D standard, the 802.1w standard recommends implementing RSTP when-
ever possible. Regardless of which standard a switch or VLAN is running, it can successfully interoperate
with other switches or VLANs.
To change the Spanning Tree Protocol for a VLAN, enter bridge followed by an existing VLAN ID (or 0
if using the flat STP instance), then protocol followed by 1d or 1w. For example, the following
commands change the protocol to 802.1w for VLAN 455 and for the flat STP instance:
-> bridge 455 protocol 1w
-> bridge 0 protocol 1w
To determine the current protocol selection for the switch or an individual VLAN, use the
command. For more information about this command, see the OmniSwitch CLI Reference Guide.
OmniSwitch 6800 Series Network Configuration Guide
Configuring STP VLAN Parameters
!
November 2004
show spantree
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