Spanning Tree Protocol

Sep 30, 2012

BPDU Guard

When BPDU Guard is enabled and a switch port receives a BPDU it stops forwarding and disables itself. It is common to enable this on a access port, usually in addition to portfast.

Dec 21, 2010

Root guard

Root Guard is a mechanism that allows the administrator to control where candidate root bridges can be connected to the network, it will basically prevent the wrong switch (say a random one just

Nov 29, 2010


Unidirectional Link Detection (UDLD) is a Cisco proprietary extension that lives to detect miss-configured and broken links between Cisco switches. It verifies that they can both send and receive data on a point-to-point

Nov 21, 2010

Loop Guard

To prevent loops that might develop if a port that should be blocking transitions to the forwarding state we have loop guard. This could happen if a port stops receiving BPDUs, maybe due

Nov 21, 2010

Implementing STP

When multiple switches exist in the same layer 2 domain you run the risk of loops forming (bridging loops). Spanning Tree Protocol (STP) detects and prevents these loops. In essence if a loop