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Does Spanning Tree Protocol have an adverse effect on VoIP?

Do you know if Spanning Tree has an adverse effect upon VoIP? If so, what is the best way to provide LAN-based switch redundancy to VoIP gateways?

Do you know if Spanning Tree Protocol (STP) has an adverse effect upon VoIP? If so, what is the best way to provide...

LAN-based switch redundancy to VoIP gateways?

Be aware that classical STP convergence time is about one minute -- it is terribly slow. There is a rapid STP or RSTP which takes a few seconds but may still be too slow for VoIP.

There are other possibilities. Some vendors have special protocols to replace STP -- for example, Extreme has Ethernet Automatic Protection Switching (EAPS), which takes about 50 milliseconds.

Another alternative way to build redundancy is using L3 switching and dynamic routing; this will have the advantage of being very fast.

Cisco's Enhanced Interior Gateway Routing Protocol (EIGRP) is fast enough or even Open Shortest Path First (OSPF), which is a little bit slower, but also good enough for VoIP -- and of course, Cisco has its own version of RSTP which they call RPVST+ and provides convergence time of less than one second after a failure.

A network with STP has one big disadvantage -- it's very hard to troubleshoot.

My suggestion is L3 switching with dynamic routing.

This was last published in October 2006

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