I don't know, how do an internal sip trunk with other ipbx:
i have site1 with shoretel pbx, and site2 with Quadro 4 x PBx,
the sites is in vpn , my site 2 has 6 phone ext : 21-27
my site 1 has 10 phones ext: 210-220
i should use sip line of quadro for my shoretel pbx and isdn line shoretel by quadro

how do i sip trunk and how configure dial plan for this on quadro?