Nat Functionality - Bay Networks Nautica 200 Reference Manual

NAT Functionality

117237-C Rev. A
In this case, each remote router provides the Nautica router with a
different IP address. The Nautica router translates between the
different addresses depending on the path being used.
NAT functions at the interface between the paths on the router
and the router engine. This allows NAT to use the path's IP
address facilitating the scenario shown in
placed at this level to allow NAT to manipulate the higher level
protocols.
The protocols used with NAT in a Nautica router are ICMP
(UDP, TCP), SMTP, POP3, HTTP, FTP, TFTP, Telnet, RLogin,
NNTP and X11.
Most of these protocols make use of UDP or TCP protocols,
which have a port field in their headers. This field is used by NAT
to select the internal addresses when a packet is received from an
external source. ICMP functions differently from UDP and TCP
and is handled separately by the NAT protocol.
to translate addresses, the router needs a table of internal
addresses with the associated external port number and path.
Some of the table entries are configured manually, for well
known port numbers (page 8-19), and some are automatically
created when a connection is made from the internal network
outside.
The following is an example of a table entry for a web server:
Internal
IP Address Port
10.0.0.1 HTTP
Where the web server's address is 10.0.0.1 and the path to the
remote router is RemotePPP.
Understanding the Technology
Figure 1-7. It is also
External
Path Port
RemotePPP HTTP
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