Can you help me?

My server chains LANs, direct and telecommunication chaining once, In addition, my LAN has ddn special lines directly, the export of telecommunications gets involved by way of lan, There is a question like this, it is when the computer surfing the Net under looks for this server, ( order ping) always go to telecommunications, turn around from ddn special line again, excuse me, How could avoid this question? ? How should this server be disposed ? Spend I it is proxy act as agent, can only bind one one net card. If dispose this server into a router, OK? ( wrap up rip of those pings and all hit back), if can have, how to do?:frowning: