ISAKMP negotiation error connecting to VPN from China?

I am attempting to connect through SonicWall Global VPN Client. It comes up with the following error much of the time when trying to connect:

"The peer is not responding to phase 1 ISAKMP requests. Starting ISAKMP phase 1 negotiation. An error occurred."

Does anyone have any idea why this occurs and how this can be fixed?

1 Answer

ISAKMP may use a too high MTU causing a split of it. Try lowering your LAN MTU or the MTU on the client system.

Also, check if NAT is done correctly and if the correct ports are open.