Any way, i think will be userful join astaro and astaro vpn options into Virtual Private Network Consortium ,Virtual Private Network Consortium -- VPNC. Ofter need to make vpn site to site with low cost adsl router, and it's difficult explain to the custumer that Astaro can't do this!
It is generally well known that Site2Site VPN solutions don't work well out of the box with products from other vendors on both ends.
But since Astaro is based on open-source quality software, it is generally very flexible. You can always modify the configuration files manually to set needed compatiblity flags etc.
Astaro uses OpenVPN for SSL and FreeSWAN/StrongSWAN/Pluto for IPSec by the way.
I've been able to make the Astaro create site to site VPNs with Watchguard, Sonicwall, and even a lowly (and I loathe them) Linksys router... I'd say it's pretty flexible.