Ok, recently I have a case, some trouble trying to connect to VPN (using Juniper’s network connect) with the LAN port. Everything works fine with the modem, I have no chance to see how it fail in the LAN port because I was never in the environment where the error takes place. The error message was something about not being able to connect to the gateway. After spending sometime plus a bit of luck, we found out that Apple’s Bonjour (Zero Configuration software) was interfering. Once uninstall, it solves the problem.
Good luck to those who has similar problem.