Single Spanning Tree (Sstp) - Foundry Networks FESX Manual

Foundry Configuration Guide for the FESX, FSX, and FWSX
NOTE: This command does not also enable STP. To enable STP, first enter the spanning-tree command
without the rstp parameter. After you enable STP, enter the spanning-tree rstp command to enable 802.1W
Draft 3.
To disable 802.1W Draft 3, enter the following command:
FESX424 Router(config-vlan-10)# no spanning-tree rstp
Enabling 802.1W Draft 3 When Single STP Is Enabled
To enable 802.1W Draft 3 on a device that is running single STP, enter the following command at the global
CONFIG level of the CLI:
FESX424 Router(config)# spanning-tree single rstp
Syntax: [no] spanning-tree single rstp
This command enables 802.1W Draft 3 on the whole device.
NOTE: This command does not also enable single STP. To enable single STP, first enter the spanning-tree
single command without the rstp parameter. After you enable single STP, enter the spanning-tree single rstp
command to enable 802.1W Draft 3.
To disable 802.1W Draft 3 on a device that is running single STP, enter the following command:
FESX424 Router(config)# no spanning-tree single rstp

Single Spanning Tree (SSTP)

By default, each port-based VLAN on a Foundry device runs a separate spanning tree, which you can enable or
disable on an individual VLAN basis.
Alternatively, you can configure a Foundry device to run a single spanning tree across all ports and VLANs on the
device. The Single STP feature (SSTP) is especially useful for connecting a Foundry device to third-party devices
that run a single spanning tree in accordance with the 802.1Q specification.
SSTP uses the same parameters, with the same value ranges and defaults, as the default STP support on
Foundry devices. See "STP Parameters and Defaults" on page 7-2.
SSTP Defaults
SSTP is disabled by default. When you enable the feature, all VLANs on which STP is enabled become members
of a single spanning tree. All VLANs on which STP is disabled are excluded from the single spanning tree.
• To add a VLAN to the single spanning tree, enable STP on that VLAN.
• To remove a VLAN from the single spanning tree, disable STP on that VLAN.
When you enable SSTP, all the ports that are in port-based VLANs with STP enabled become members of a
single spanning tree domain. Thus, the ports share a single BPDU broadcast domain. The Foundry device
places all the ports in a non-configurable VLAN, 4094, to implement the SSTP domain. However, this VLAN does
not affect port membership in the port-based VLANs you have configured. Other broadcast traffic is still contained
within the individual port-based VLANs. Therefore, you can use SSTP while still using your existing VLAN
configurations without changing your network. In addition, SSTP does not affect 802.1Q tagging. Tagged and
untagged ports alike can be members of the single spanning tree domain.
NOTE: When SSTP is enabled, the BPDUs on tagged ports go out untagged.
If you disable SSTP, all VLANs that were members of the single spanning tree run MSTP instead. In MSTP, each
VLAN has its own spanning tree. VLANs that were not members of the single spanning tree were not enabled for
STP. Therefore, STP remains disabled on those VLANs.
7 - 56 © Foundry Networks, Inc. December 2005