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FXO Ports under SRST Mode

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Dec 5th, 2005
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I am trying to configure some FXO ports (loop-start, non-DID) to accept incoming calls and route them to a specific DN when the router (2851) goes into SRST mode. I have the MGCP configuration up and running and the ports work under Call Manager operation. However, in SRST mode the incoming calls hear one ring, about 15 - 20 seconds of silence and then the call drops.

Obviously I am missing something in the configuration but I'm rather new to SRST configurations. I've tried the default-destination command to no avail. It seems that there may be some dial-peer configuration missing.

How should this be configured? Remember these are simple ring-in lines (no calling/called number information is available.)


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agopala Mon, 12/05/2005 - 17:34
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can you paste your configs here. If possible, also send me a 'debug voice ccapi inout' and debug vpm signal when your router is in SRST mode.


stephen.kruse Wed, 12/07/2005 - 14:14
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Unfortunately, we had a set-back on this system involving passwords. To make a long story short, we had to blow out the config and rebuild the system. After doing so, the default-destination command actually did the trick.

ewmcg Mon, 12/05/2005 - 20:39
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I'm having a similar problem on a 2801 router in SRST mode. When the router gets the call it hangs the FXO port after the call come in. The port remains lit after hanging up the call. Do you have this problem as well on your 2851 router where the port is staying lit?

stephen.kruse Wed, 12/07/2005 - 14:17
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Not yet on the 2851. However, I have noticed that this happened on a 2651XM at another site. I can't confirm at this time, but it seems that it may be related to a network outage. After recovering from the outage, the lines that were on calls may not have properly disconnected before the switch-over. Unfortunately, on loop-start lines (in this case from the CO) there is no disconnect supervision on the external end so the call is only disconnected when the internal phone hangs up.

b.athanasiadis Wed, 12/07/2005 - 19:46
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I am fairly new to SRST myself and I have been working on this very issue. By default the router is configured for two-staged dialing ie when you call the PSTN number you will get a dial tone once the FXO connects. You can then dial the extension of your ephone.

If you do not want to use two stage dialing you will need to use Private Line Automatic Ringdown (PLAR).

Also when testing make sure you are in SRST mode. This will be indicated by a message appearing on the ephone once it is registered with the gateway.


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