Address limitedness IP V. 4 be problem in global network or Internet. To maximise address user IP that given by internet service provider (ISP) can used network address translation or Nat. Cisco implementation with use RFC 1631. Nat make network that use local address (private), Address there may not be any in table routing internet and Specialize for network local/intranet, Can communicating to internet by way of borrow address IP internet that allocated by ISP.

Two types NAT

Two types NAT static and Dynamic both can be used separately also concurrent.

 

Static

Translation static happen when a local address (inside) at map to a global/internet address (outside). Local address and Global mapped one opponent one according to static.

Dynamic

 

Nat with pool (group)

Translation dynamic happen when router NAT at set to realize local address that must translation, And Group (pool) global address that be used to linked to internet. Process NAT dynamic this can Map Several local address group to several global address groups

NAT overload

Amount of IP local/internal can translation to one address IP global/outside. This matter is very save allocation user IP from ISP. Sharing/use with one address IP this use method port multiplexing, or Change port to packet outbound.

Components NAT

NAT can let pass local network address (‘private’) aim network ‘public’ like internet. Address ‘private’ that present in local network /" Inside" , Send package passes router NAT, Then changed by router NAT be IP address ISP so that  package can sustained pass by public network or internet. Initially facilities this only available in gateway pass-through firewalls. But now available at all router Cisco.

When should NAT used?

Use NAT if:

A. You want connection to internet and Your hosts/computers don't have address IP global.

 

B. You change to ISP new and You are compelled to use address IP from ISP new For your network.

NAT used to finish address gift problem IP

Technology NAT make possible address IP local/’private’ linked to public network

Like internet. A router NAT laided between local network (inside network) and public network (outside network),  and translate local/internal address is address IP global unique before send package to network outside like internet. With NAT, internal/local network, Will not be seen by outside/internet world. IP local quite a lot can be letted pass to only through translation to one IP internet public/global.