Configuring Linux as a router with NAT support is not difficult but it can be
confusing. What makes the job difficult is making sure the connection to the
Internet is secure. The ipchains configuration is the first step.
Additional steps are required if the router is running other services such as
DNS, the Apache Web server, or an FTP server.
A D V E R T I S E M E N T
The /etc/inet.conf file is typically used to designate how
IP-based services will be started if a request comes from another computer. The
telnet and FTP services can be handled using inet.conf. This
article will not go into any detail oninet.conf, but online help is
In addition, certain services will be started when Linux boots. The Apache
Web server and the DNS server, BIND, are normally started this way. By default,
these services, and the ones started via inet.conf, will work with
any network adapter on the computer but it is possible to configure applications
to work with specific adapters. For example, the Apache Web server keeps its
configuration files in /etc/httpd/conf. The httpd.conf
and access.conf files control what computers and what adapters can
be used with the web server. If a statement like Listen 220.127.116.11:80
is in the configuration files then the Web server will ignore other adapters,
such as an Ethernet adapter connected to the Internet, and only use port 80 on
the adapter associated with the IP address 18.104.22.168. The linuxconf
program can be used to set up this configuration instead of dealing with the
configuration files directly.
Another possible option is to set up the DNS server so it can service the
local network and transparently forward Internet requests to an ISP's DNS
server. This makes configuration of local workstations easier but it requires an
understanding of BIND.