3Com WX2200 3CRWX220095A Switch User Manual

The purpose of the Spanning Tree Protocol (STP) is to maintain a loop-free
network. A loop-free path is accomplished when a device recognizes a
loop in the topology and blocks one or more redundant paths.
Overview Mobility System Software (MSS) supports 802.1D and Per-VLAN Spanning
Tree protocol (PVST+).
MSS uses 802.1D bridge protocol data units (BPDUs) on VLAN ports
that are untagged. However, each VLAN still runs its own instance of
STP, even if two or more VLANs contain untagged ports. To run a
single instance of STP in 802.1D mode on the entire switch, configure
all network ports as untagged members of the same VLAN.
MSS uses PVST+ BPDUs on VLAN ports that are tagged. PVST+ BPDUs
include tag information in the 802.1Q field of the BPDUs. MSS runs a
separate instance of PVST+ on each tagged VLAN.
STP does not run on MAP access ports or wired authentication ports and
does not affect traffic flow on these port types.
When you create a VLAN, STP is disabled on the new VLAN by default,
regardless of the STP state of other VLANs on the device.
The IEEE 802.1D spanning tree specifications refer to networking devices
that forward Layer 2 traffic as bridges. In this context, a WX switch is a
bridge. Where this manual or the product interface uses the term bridge,
you can assume the term is applicable to the WX switch.