A customer of ours is setting up an ISA-Cluster in private network address range and we have to build a VPN connection with them. There is no way avoiding NAT-T and this is where we get to a problem:
in IKE request there is a field ENCAPSULATION_MODE where there should be a value of 3 for NAT-T if you go by the book (RFC3947).
However Ciscos and it seems Microsoft ISA still send historical value of 61443 which is accepted by OpenBSD (tolerant, good). But - there is no way to make OpenBSD send a request with ENCAPSULATION_MODE = 61443 and the "standard" value 3 is rejected by Microsoft ISA.
Anybody knows a solution to this?
It'd be nice to hear of a patch for MS ISA allowing it to accept the "3"...
Update: "The other side" has MS ISA 2006 Enterprise. "Our side" has OpenBSD 4.5.