HP-UX IPFilter Version 15.01 Administrator's Guide

bimap: Bidirectional Mapping
The bimap keyword creates two map entries for the rule: one for inbound and one for outbound.
Unlike the map keyword, an initial inbound packet is not required to create the outbound rule.
The bimap keyword allows IPFilter to map IP addresses bidirectionally. You can use this when
you want the IP address of a particular device on the NAT-supported system to appear to have
a different IP address outside the system. For example:
bimap lan0 192.168.1.1/32 -> 20.20.20.1/32
In this example, the interface with IP address 192.168.1.1 on the NAT-supported system appears
to have the IP address 20.20.20.1 outside the system.
66 Configuring and Loading Network Address Translation (NAT) Rules