Passing alert_info

Hey all, first post so excuse any omitted detail!

Our Asterisk box at site A is connected to another at site B via IAX2 trunk (no site-to-site link involved - it just routes over the internet). Site A doesn’t have a direct connection to the PSTN, but site B does, hence the trunk. This is an interim measure for us until we can get a trunk to a third party provider with a PSTN gateway so we don’t keep having to use site B’s (which isn’t possible long-term).

On a side note here: any suggestions for SIP/IAX2 trunk providers in the UK? I’ve so far heard of Gradwell, Callsure, Adepteo, and AQL - anyone with experience of any of these?

Anyway back to my original question. Inbound call routing is:

  1. Call to one of our public numbers
  2. Arrives at PSTN gateway at Site B
  3. Site B sends to a custom destination which is actually an internal extension or ring group on the PBX at site A (didn’t get chance to play with DUNDi to do this properly)
  4. Call is answered at Site A

This works fine, but I can’t see a way to set alert info on this route to what I need to make my phones ring properly. The inbound routes at Site B set alert info properly, but it’s like it doesn’t make its way down the IAX trunk to Site A. The trunk config has set


Could that be part of the issue?
Thanks in advance to anyone who can point me in the right direction.