One-to-One Translations

Use static NAT rules to make one-to-one translations between either a single pair or multiple pairs of addresses. Most commonly, static NAT rules are used to translate an advertised address for a public server to a different address.

A static NAT rule translates either the source or destination addresses in a packet. In most cases, this means that you will need to define two NAT rules to:

• Translate the source address when the packet is flowing in one direction.

• Translate the destination address when packets are flowing in the other direction.

As an example of static NAT rules in one-to-one translation, assume that your public web server has an address of 10.0.0.1 (defined by the address object "private_www") and you want to allow access to this web server through the public address 199.190.177.1 (defined by the address object "public_www"). Assume also that the address Internet represents Internet addresses. To do this requires two static NAT rules, as shown in the table below

• The first rule specifies that the destination address public_www (199.190.177.1) is the translated destination address private_www (10.0.0.1). This NAT rule handles packets flowing to the web server.

• The second rule specifies that the source address private_www (10.0.0.1) is the translated source address public_www (199.190.177.1). This NAT rule handles packets flowing from the web server.

  Table 7-1 Static NAT Rules

  Type of NAT Rule	Source	Destination	Translated Source	Translated Destination	Comment
  STATIC	"Internet"	"public_www"	"Internet"	"private_www"	Packets to server
  STATIC	"private_www"	"Internet"	"public_www"	"Internet"	Packets from server