Using Asterisk as PRI to PRI gateway

We have been fiddling with asterisk for a while and are now wondering how we should do this:

I need to ‘share’ one PRI line between two machines (one fax server and a test pbx system). I have an spare Asterisk machine with a 4 port PRI card in it.

I tried to configure it to act as a gateway. I connected one of the card’s interfaces to our providers line, one to the fax server and one to the test PBX. In the extentions.conf I configured the spans to forward the calls from my machines to the provider using the Dial command. E.g.:

exten = s,1,NoOp()
exten = s,2,Dial(${span_1}/${EXTEN},,r)

This ‘seems’ to work, but I get some strange results…

[]Roughly half the faxes send this way fail with all kinds of errors, if I hookup the provider’s PRI directly to the fax server almost al faxes go through perfectly.[/]
[]The test pbx system has Siemens SIP phones connected, when I ‘open’ a line on them, they seem to request an outside line with dialtone. when connected directly to the provider, I can dial out just fine. When connected via the Asterisk gateway, the logs show me that the number I’m trying to call is somehow lost, the ${EXTEN} parameter is empty, and dialing fails[/]

Any help is appreciated!

FAX problems would hint at either using an inappropriate codec, or CPU loading issues.

I’d suspect a problem with the “dialplan” in the phone itself, for the other problem. The provider may be configured to support overlap dialling.

Hey David,

Thanks for the response!

This might be being terribly optimistic here, but… I don’t want to have to deal with codecs on the Asterisk box… my fax server has a fancy Dialogic fax board, and I would like to “bridge” the outside line to it… Without any knowledge of these things, I would say that ‘bridging’ the outside PRI to the inside PRI should solve all my issues… But I don’t know if there is such a thing…

Is that a Digium PRI card?


Yep, it’s a TE410P

Doest that make any difference?


Means it’s the kind of thing we could help troubleshoot with you, though it might be under an OSS Subscription.

Give our Support team a ring: