Rockwell Automation Publication 1783-UM006A-EN-P - May 2014 301
Chapter 9
Configuring Spanning Tree Protocol
This chapter describes how to configure Spanning Tree Protocol (STP) on your
access point.
Understanding Spanning
Tree Protocol (STP)
STP is a Layer 2 link management protocol that provides path redundancy while
preventing loops in the network. For a Layer 2 Ethernet network to function
properly, one active path can only exist between any two stations. Spanning-tree
operation is transparent to end stations, that cannot detect whether they are
connected to a single LAN segment or to a LAN of multiple segments.
When you create fault-tolerant internet-works, you must have a loop-free path
between all nodes in a network. The spanning-tree algorithm calculates the best
loop-free path throughout a Layer 2 network. Infrastructure devices such as
wireless access points and switches send and receive spanning-tree frames, called
bridge protocol data units (BPDUs), at regular intervals. The devices don’t
forward these frames but use them to construct a loop-free path.
Multiple active paths among end stations cause loops in the network. If a loop
exists in the network, end stations can receive duplicate messages. Infrastructure
devices can also learn end-station MAC addresses on multiple Layer 2 interfaces.
These conditions result in an unstable network.
Topic Page
Understanding Spanning Tree Protocol (STP) 301
Understanding Spanning Tree Protocol (STP) 301
Access Point/Bridge Protocol Data Units 302
Access Point/Bridge Protocol Data Units 302
Election of the Spanning-tree Root 304
Spanning-tree Timers 304
Creating the Spanning-tree Topology 305
Configuring STP Features 308
STP Configuration Examples 310
Root Bridge with VLANs 313
Displaying Spanning-tree Status 318
STP is available only when the access point is in bridge mode.
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