Network address translation
Network address translation (NAT) is the process of
modifying IP address information in packet header while it is in transit across
a traffic routing device. The simplest type of NAT provides a one to one
translation of IP addresses. Referred to as basic NAT, it is also referred to
as one-to-one NAT. In basic NAT, the ones that need to be changed include the
IP addresses, IP header checksum and any higher level checksums. The rest of
the packets are not changed in any way.
Advantages: Not every inside host needs outside access at
the same time, therefore, it can get away with using small pool of globally
unique address to serve a relatively large number of privately addressed host.
Another advantage is that network address translation has
the effect of hiding the inside structure of a network. With this, the internal
addresses are not visible to external host.
www.cisco.com
Port address translation
Port address translation (PAT) is an extension to network
address translation (NAT). It allows multiple devices on a local area network
(LAN) to be mapped to a single public IP address. The main purpose of PAT is to
conserve IP addresses.
Techrepublic.com
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