I'm having a problem with a Vigor 2710n not passing SIP traffic over a Lan to Lan VPN, strangely this configuration worked fine with a 2820n at both ends but not with a 2710n VPN to a 2820n so I can only assume it's the 2710n at fault. All other traffic such as ssh, rdp etc. is passed over the VPN without a problem. Would be grateful for any advice solving this problem.

Switched to IAX trunk and turned qualify off and now works fine, not sure why qualify fails as ping from each end is only 50ms.

Same here. Inbound calls work, outbound not. Maybe sip alg? 2820n fine.