HiWe are having a RE-invite issue with Grandstream 200/2000 phone that  we have tested.  We want to deploy them to 1000+ of our remote customers.We are using inGate firewall and sipX IP PBX.  We have 3 networks. One behind the firewall, one on the our outside network and a phone connected to an AT&T DSL/router.  And for further testing we have an standalone AT&T phone.All the phones register to the sipX and all the phones are about to make outbound calls. BUT phone connected to Remote AT&T DSL/router although registered will not make outbound calls.  We have determined that Grandstream phone fail to RE-invite, which they must do to comeplete Remote phone to Remote phone and Remote phone into our network.This is the problem:  Remote GS phone on DSL line registers to sipX behind inGate in Chicago.  If we try to make a call to phone connected to sipX and to a Remote phone in Texas.  We are using wireshark  pcap. We see the call packetts get to the sipX but the phone will not autheniccte and sends a 403 error.Snom 300, 320 and 360 work immediately.Are the Grandstream phones capable to issue RE-invites?  if yes.  HOW ?r