Asterisk to Asterisk Ring Groups / Follow Me setup issue

Hi, I’ve been playing around with * for a couple of years and have just attempted to setup two boxes and get them working via an IAX2 link.

Everything is working really well, but I’m having trouble over-coming a problem with a ring-group/follow-me setup on one box which rings extensions on both * boxes!

I understand why this is happening, I’d just like to know if anyone has a thought on how to overcome.

Box A: * 1.6 with FreePBX 2.7
NAT’d with a Dynamic IP Address
X100P SE FXS connected to PSTN Line
3 SIP Extensions - not always on / connected

BOX B: * 1.4 with FreePBX 2.7
Public IP Address
5 SIP Extensions - not always on / connected
~ 50 miles away from Box A

When the PSTN line rings (connected to Box A) it should ring all 3 SIP Exten on that box, plus 1 on Box B. However, when Box B exten is offline it immediately gets picked up and sent to that VM.

What I’m looking at doing is having Box B ring for 15s even if the SIP Exten is offline so that Box A has a chance to send to local VM.

I thought a Vitrual Exten would work with a follow-me (it has a Ring-Time setting which I set to 15s and setup a VM so this wasn’t skipped) but this didn’t do a thing - it still got send through to VM immediately.

My concern is that in order for this setup to work, Box B SIP would always have to be online so the exten on Box A have a chance to ring.

Any thoughts?