HP-UX IPSec version A.02.00 Administrator's Guide

HP-UX IPSec and IPFilter
IPSec Gateways
Chapter 6198
IPSec Gateways
You can configure IPSec to encrypt and authenticate traffic to a gateway
between two end hosts. A configuration that encrypts IPSec packets to a
gateway is called an IPSec tunnel.
IPFilter can coexist with IPSec tunnels with out conflict. However, you
must configure IPFilter to allow IPSec traffic to and from the gateway
instead of the end node. The IPFilter rules for the UDP/500 and protocol
50/51 traffic must be passed to and from the gateway IP address rather
than the end node IP address.