There are some consequences that should be done if we are to our servers in the LAN can be recognized by the user on the Internet. Servers are generally want to open to the Internet usually primarily to send and receive email from/to the Internet.
Some small entrepreneurs may be building a Web server on the LAN. Usually for traffic is great, the Web server would be better placed on hosting services on the Internet.
There are some fundamental difficulties which led to the laying of LAN servers to be accessed by users on the Internet is becoming a bit difficult, namely:
- Router ADSL (Asymmetric Digital Subscriber Line) usually serves as a NAT (Network Address Translation)/firewall between the network LAN to the Internet. Consequently the only traffic from the LAN network to do the Internet but not too easy for the traffic from the Internet to a server on the LAN.
- ADSL Networks generally use a dynamic IP address. The consequences will be more difficult for users on the Internet to find out the IP address of the router ADSL because is not fixed.
Surely there is a solution that allows us to put a server behind a router ADSL. These solutions include:
- Use the services of Dynamic DNS. In principle, a Dynamic DNS service allows all routers on the Internet/machine.
That does not have a static IP, dynamic IP only has the always fickle, can enlist the services of Dynamic DNS and register the hostname to a dynamic IP address. So that's very simple, because the hostname can be fixed with a Dynamic DNS service so users on the Internet no longer need to know the IP address is dynamic (changing) to contact ADSL router, but enough to know hostname listed through services of Dynamic DNS.
- Because the servers we build usually are behind a firewall or NAT mechanism built-in router ADSL, we should use the ADSL router at facilities that allow all traffic that is directed to the Internet and our server so that it can forward the ADSL router directly and do not run any services over ADSL router. By using the facilities that allow for forwarding all packets to the ports on the ADSL router gets redirected to the server on the LAN, making LAN server is open to all connect to Intrenet. This facility is known as the DeMiliterized Zone (DMZ). Consequently we have to make a strong defense on our servers in order to be safe and Internet attacks.
Other means that may be done so that our servers are relatively safe and Internet attacks is to open certain ports, for example, email SMTP, POP3 or IMAP that is opened. That way, only traffic to a specific port that will be forward to servers on the LAN. Other defences are performed by the firewall on ADSL router we use. This technique is known as port forwarding.
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