SSL VPN used in a VPN gateway, trouble accessing remote network from other networks going through the gateway. Any remedy?

Question

A remote vendor used his SSL VPN connection (login and OVPN file) in a VPN gateway. His goal is for various machines on multiple networks on his end to access my network through this VPN gateway. 
 The vendor is able to reach my network from the gateway, however other devices on other networks (different subnets) going through the vpn gateway cannot. 
 Is this a limitation of the SSL tunnel, or a bad config in the remote vendor's setup? 
 I did not realize he wanted to do this kind of setup. I suspect the proper fix is to set up a site to site vpn.

ErickJan · Answer

Hi David, 
 Thank you for reaching out to Sophos Community. 
 Can we verify if the " different subnets" are already included on the SSL VPN Permitted network resources?

emmosophos · Answer

Hello David, 
 Adding to what Erick mentioned, I am unclear about your setup or the VPN Gateway used. 
 However, suppose the vendor can reach out to your network from the VPN gateway. In that case, you could compare if you see traffic arriving to your network (passing the Firewall) from the other subnets by doing a tcpdump in the Sophos Firewall; if you see traffic arriving to the Firewall but being dropped by the Sophos Firewall, then you can troubleshoot further, but if you don't see the traffic arriving most likely your vendor is incorrectly config their end. 
 I have never heard of this type of setup. I believe a site-to-site VPN would be a better approach if the vendor has different subnets and they want to access subnets on your Network. 
 Also feel free to share a draft of how this setup is currently done if what I mentioned above doesn't fit the current setup. 
 Regards,

SSL VPN used in a VPN gateway, trouble accessing remote network from other networks going through the gateway. Any remedy?

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