Most consumer grade "routers" and their DMZ feature will only support a
single IP address. As such, only ONE computer will be able to receive
the IPIP packets. As such, I see that you have a few options:
1. Use a VPN to tunnel IPIP traffic into your system (no DMZ access
needed; possibly no port forwards required either). Can be an SSL-VPN,
IPSEC VPN, etc. Search the archives here in this list to see who's
offering such services for free or options with commercial providers
2. You don't mention what kind of computer your brother is running
but if it can enable routing on it, you should able to configure his
machine to accept and FORWARD the IPIP packets to your machine. This
obviously will mean that his machine will need to be turned on and
working when you want to use the AMPR network
3. Replace your router with a device that supports more advanced
routing. This could be anything from a home brewed Linux/Free/OpenBSD
computer with a few network ports, a Microtik router, RouterBoard
computer, a Cisco/Juniper/etc commercial router, etc. You'll find lots
of users on this AMPR list doing things this way with a variety of devices.
4 .don't use IPIP for your connection to the AMPR system. Instead
use AXUDP to develop communications to remote stations. This will
require port forwards on your router to work. It should be noted that
not all stations support AXUDP as a forwarding mechanism so you will be
limiting your access to the AMPR system
There might be other options out there that people can comment on here too!
--David
KI6ZHD