Avoid ARS routing loops

[petr.necas]

We have a customer that uses various different DID numbers. I programmed mappings to the actual extensions in the Direct Inward Dialing Service. This works fine, but in case there is an incoming call with a DID number that is not programmed in the Direct Inward Dialing Service, the PBX then looks into the ARS table (there is no dialing prefix such 0, because the customer does not want to use it) and routes the call back to the trunk. The SIP peer then routes the call back to the PBX, the PBX routes the call back to the SIP peer, and so on.

Is there any way to avoid these trunk loops?

[acejavelin]

So your customer is not using a 0/8/9 for an outbound prefix? That isn't really a supported setup and can potentially cause all kinds of issues, like you see now... You are probably just seeing the beginnings of problems, they will likely multiply. :/

How to avoid it?

Change the COR of the trunks so they can't dial out.

Change your Trunk Service to absorb some digits, adjust DID routing table, and make it an invalid outbound call. For example, if your DID is 343-1234, absorb 3 and have it route in the DID table off of 1234, if 1234 does not exist it will route to the invalid number intercept since "1234" will (should) not be a valid ARS match.

Add all DID numbers to the DID routing table, regardless if they are in use or not, and set ones that are not being used to fixed point (speed call to extension, RAD, voicemail, AA, or whatever).

Probably more options, that's just off the top of my head.

[petr.necas]

Hi acejavelin, thank you for your reply.

So your customer is not using a 0/8/9 for an outbound prefix?

Yes, that was a strict requirement from the customer. I was not too happy about it, but anyway....

That isn't really a supported setup and can potentially cause all kinds of issues, like you see now... You are probably just seeing the beginnings of problems, they will likely multiply. :/

Hopefully it will not be that bad ;-) Sometimes some "hacking" is needed to make the system to what it suppose to do.

Finally in the trunk Attributes I set not to absorb any digits but to insert some dummy prefix e.g. 0# and then then updated all records in the Direct Inward Dialing Service to prefix with 0#, in ARS there is no Route starting with 0# so any attempt to route back to the trunk fail and give the caller reorder tone. It seems it works this way but I will do some more testing.

[acejavelin]

Adding digits should work just as well... As long as it doesn't match an ARS string you should be good to go.