The Spanning Tree Protocol (STP) eliminates Layer 2 loops in networks, by selectively blocking
some ports and allowing other ports to forward traffic, based on global (bridge) and local (port)
parameters you can configure.

STP related features, such as RSTP and PVST, extend the operation of standard STP, enabling you
to fine-tune standard STP and avoid some of its limitations.

You can enable or disable STP on a global basis (for the entire device), a port-based VLAN basis (for
the individual Layer 2 broadcast domain), or an individual port basis.

Configuration procedures are provided for the standard STP bridge and port parameters as well as
features listed in

Table 90

Configuring standard STP parameters

TurboIron X Series devices support standard STP as described in the IEEE 802.1D specification.

By default, each port-based VLAN on a device runs a separate spanning tree (a separate instance
of STP). A device has one port-based VLAN (VLAN 1) by default that contains all the device ports.
Thus, by default each device has one spanning tree. However, if you configure additional
port-based VLANs on a device, then each of those VLANs on which STP is enabled and VLAN 1 all
run separate spanning trees.

If you configure a port-based VLAN on the device, the VLAN has the same STP state as the default
STP state on the device. Thus, on Layer 2 Switches, new VLANs have STP enabled by default. On
Layer 3 Switches, new VLANs have STP disabled by default. You can enable or disable STP in each
VLAN separately. In addition, you can enable or disable STP on individual ports.