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5. Configuring the FrameSaver SLV Router
9128-A2-GB20-80 September 2002
5-5
Network Address Translation
Network Address Translation (NAT) is used when a private network’s internal IP
addresses cannot be used outside the private network. IP addresses may be
restricted for privacy reasons, or they may not be valid public IP addresses.
The router provides NAT as described in RFC 1631,
The
IP Network Address
Translator (NAT).
NAT allows hosts in a private (local) network to transparently
access the external (public or global) network by using a block of public addresses.
Static mapping enables access to selected local hosts from the outside using
these external IP addresses.
Traditional NAT and Network Address Port Translation (NAPT) are supported.
When both NAT and NAPT are enabled, one-to-one NAT mapping is performed by
translating a range of assigned public IP addresses to a similar-sized pool of
private addresses, followed by many-to-one NAPT bindings. Up to 254 IP
addresses can be allocated for NAT usage.
IP Options Processing
The NAT and NAPT functions handle and process the IP datagrams with options
set as described below. No command is available to set IP options.
The router does not process (and drops) any IP datagrams with the following IP
options:
Loose source and record route (type 131)
Strict source and record route (type 133)
Security (type 130)
Stream ID (type 136)
The router does process IP datagrams with the following IP options, but does not
provide its IP address or timestamp information in the response message:
Record route (type 7)
Timestamp (type 68)
Applications Supported by NAT
The router supports the following applications and protocols:
FTP
HTTP
Ping
RealPlayer
Telnet
TFTP