Header Only - DO NOT REMOVE - Extreme Networks

Network Loop through VoIP Phone

  • 17 December 2015
  • 5 replies

Userlevel 6
Last week we have a network loop caused by a VoIP Phone - mitel 6865i. Someone plugin both ports of the phone into the wall / switch. Because the 2 port switch in the phone forward data frames but filter out BDPUs frames, so Spanning Tree have no change to detect this loop.

my question is now, is the voip phone complaint to ethernet standard ? Can i force mitel to change this behaviour to a more ethernet standard behaviour - means either passes BDPU through or process that BPDUs (have STP) ?

Whats your oppinion ??

5 replies

Userlevel 7
You may want to try ELRP: easy to configure and maintain, and it will protect you against that kind of problem.
Userlevel 7
What switch models are in your network?
Userlevel 6
If it is an Extreme switch then you can also set a broadcast packet per second limit on those voip ports.... we set to 100 pps.... It does not stop a loop but limits the effect it has on the network and you get an immediate trap from port where the loop is and makes it easy to spot and react to...

configure port xx rate-limit flood broadcast 100

this can also be done on mcast and unknown mac-addresses .... we only set the broadcast packets limit.. As a pure layer 2 Ethernet metro service provider we set this on all customer facing access interfaces and adjust the pps according to the service size... This gives us a trigger if anyone of our clients has a loop going on that is leaking back out into our network...
Userlevel 3
Not to hijack the thread, but I have a related question along the same vein...

We have a customer that needs the edge-safeguard functionality of STP, but also has VoIP phones. Can ELRP be used along with STP?

For some reason, I was thinking that they could not be used together, although I haven't found any documentation to that effect.

Userlevel 6
Hi Bill, i decide to use broadcast limits AND mac-lock on a edge-oport along with RSTP - to be informed and to limit broadcast-storms if some do silly things which is not detect by RSTP.