we have one draytel account with 5 trunks.

Do I need to configure IPPBX SIP trucks 1,2,3,4,5 with the same registration details? Draytel support seemed to suggest I just needed to configure one SIP but I don't think that can be correct.

and on each extension tick use SIP1,2,3,4,5 but not 6, then the PSTN
so that if SIP's are down it will finally dial out on the PSTN POTS line?

Many Thanks

I'm sure you have sorted this out by now, but just in case...

I'm only answering from my knowledge of SIP rather the Vigor IPPBX (which I don't yet have). I assume the 5 trunks you have from Draytel simply means your account can handle up to 5 simultaneous calls. In which case, just register a single trunk in the IPPBX to the Draytel account.

Unless the IPPBX is somehow limited to only a single simultaneous call on a trunk, but that is entirely against how SIP is supposed to work and I cannot believe Draytek would have got that so wrong. In any case, multiple simultaneous registrations from the IPPBX to the Draytel account is unlikely to be the solution.