Configuration Guide User guide

FastIron Configuration Guide 1151
53-1002494-02
STP feature configuration
Single Spanning Tree (SSTP)
By default, each port-based VLAN on a Brocade device runs a separate spanning tree, which you
can enable or disable on an individual VLAN basis.
Alternatively, you can configure a Brocade 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 Brocade
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 Brocade devices. Refer to “STP parameters and defaults” on page 1088.
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 Brocade 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.
Enabling SSTP
To enable SSTP, use one of the following methods.
NOTE
If the device has only one port-based VLAN (the default VLAN), then the device is already running a
single instance of STP. In this case, you do not need to enable SSTP. You need to enable SSTP only
if the device contains more than one port-based VLAN and you want all the ports to be in the same
STP broadcast domain.
To configure the Brocade device to run a single spanning tree, enter the following command at the
global CONFIG level.
Brocade(config)#spanning-tree single