With Answer Key (на англ. яз. ) Grammar Express Basic: For Self-Study and Classroom Use:

Instead of using fairly expensive third party solutions such as Cisco PIX etc, a lot of smaller companies and personal users have chosen to go with these solutions instead. One of the main reasons is that it is cheap, and secure. It requires an old computer, a fairly new Linux distribution which you can download for free from the Internet, a spare network card or two and cabling. This chapter will describe a little bit of the basic theory about NAT, what it can be used for, how it works and what you should think about before starting to work on these subjects. What NAT is used for and basic terms and expressions Basically, NAT allows a host or several hosts to share the same IP address in a way. For example, let's say we have a local network consisting of 5-10 clients. We set their default gateways to point through the NAT server. Normally the packet would simply be forwarded by the gateway machine, but in the case of an NAT server it is a little bit different. NAT servers translates the source and destination addresses of packets as we already said to different addresses ...»