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Possibile to monitor when a POTS phone line goes down

I wonder if it is possible to monitor when a POTS phone line goes down.

I have a Cisco 2811 router with an FXO card that I am using as an e-911 gateway for our VOIP phone system and I want to be alerted if the analog phone line ever goes dead. I know that there are devices for actual (fire/burglar) alarm systems that can sense when a phone line is cut (by a burglar perhaps) by sensing loss of voltage from the phone company.

It would be nice to be alerted if the phone line you are using for 911 ever goes down

Brian Mangan

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mdriskell

It has been a while but I believe that the router is aware of the change in that interface. Are you monitoring the interface now? Can you test pulling the phone line?

lgca.mangan

I am monitoring that interface, and if I pull the phone line, nothing happens. By "nothing happens", I mean nothing shows on the router as down, nothing shows in NPM as changed. The only way "something happens" is if I administratively shut down the interface...

Router(config)#voice-port 1/1/0
Router(config-voiceport)#shut
Router(config-voiceport)#end
Router#show voice port 1/1/0

Foreign Exchange Office 1/1/0 Slot is 1, Sub-unit is 1, Port is 0
Type of VoicePort is FXO
Operation State is DOWN
Administrative State is DOWN
The Last Interface Down Failure Cause is Administrative Shutdown

mdriskell

If the router is unaware Solarwinds will be unaware. Sorry but it has been about 8 years since I dealt with an FXO port on a Cisco so I'm going from memory.

If the line is unplugged and you try and start a call do you get an error?

lgca.mangan

I can't unplug and try a call... since it's VOIP, there may be some backup path and the call could proceed. My boss said "don't do that".

Looking at the MIB from that device, I discovered some interesting objects that I thought I might create a custom poller for

cvaIfFXOTipGround This object contains the incoming tip ground indication.
                 It is only valid when the cvaIfFXOCfgSignalType is
                 fxoGroundStart. If the object is true, then the interface
                 is detecting a tip ground at the interface; otherwise,
                 it doesn't.
So I set the signal type of the interface to fxoGroundStart, but the value of cvaIfFXOTipGround did not change.. bummer