I have one unusual scenario where two gateways, lets say GW A and GW B, have established S2S VPN tunnel, but still I have a requirement from some customers located behind GW A to have RAVPN connectivity to some servers located behind GW B. S2S VPN is running smoothly, but RAVPN could not be established. I tried to exlude HTTPS and IKE services from the S2S VPN community, but without any success. I checked the logs where I see GW B is rejecting the phase 1 from RAVPN saying:
Main Mode Failed to match proposal: Transform: AES-256, SHA1, Pre-shared secret, Group 2 (1024 bit); Reason: Wrong value for: Authentication Method
RAVPN is using different proposal than S2S and it seems that GW B cannot differentiate between IKE messages generated by GW A and between IKE generated by side-A customers since they are coming from the same public IP address.
I know this is quite unusual to have such scenario, but I am wondering is there some kind ow workaround have to handle such a situation?