How do I disable IP Forwarding?

For HP-UX 10.x, one uses nettune to set the variable ip_forwarding to 0.
For HP-UX 11.x, one uses ndd to set the variable ip_forwarding to 0. For
HP-UX 11.x, this tune can be placed in the file /etc/rc.config.d/nddconf
and will then be applied automagically on every reboot.