Problem with DMZ

[Gocha]

Hey guys, I know I've been asking a lot of question, but I have no idea how networks work.

The problem is the following

To be able to connect to some games I need to enable DMZ, so I went to the router configuration and enable it, but there are 2 problems with this:
1.- it doesn't work, I cant join games from other users on WWP
2.- when I set the "enable DMZ" option it asks for an IP to enable DMZ, so I set it to xxx.xxx.xx.98 as seen on the image attached, but on the list at the side of the IP there is no device with that IP, and there is only 1 device that is "unknown" which I asume is maybe the dreamcast, but that device has another IP, so, should I set the DMZ to the IP of the "unknown" device, or keep it on .98? of the last option is the correct one, why can't I connect to WWP?

As far as I know I can also use port forwarding to configure ech game manually, but when I try it asks for the device IP, so again IDK if I should use .98 or the one that appears on the list.

Questions:
is it normal for the dreamcast to not appear on the list?
how can I make sure of my dreamcast IP? (I know there is a way ussing Q3 arena, but as I posted before that game is not working for me)
If the dreamcast is NOT on .98 is there a way to change that?


EDIT:
After all the help I had with the user megavolt85 I was able to solve the problem and I'm now able to play games that need DMZ. If anyone finds this post and has the same problem that I had, please check for the answers given bellow, but in short my problem was that I had my modem connected to a router and that router didn't have a DMZ configurated, to do so I had to set the WAN IP of my router to Static IP, and then access the company provided modem to set the DMZ at the same static IP of the router. Well, al least that´s what I think I did, but reading the posts bellow you can follow it step by step.

[Village Inn]

Hi Gocha. Afaik it is USUALLY xxx.xxx.x.98 that needs to be in DMZ. You might try turning your firewall down if it's not already. My DreamPi didn't like to work until I turned my firewall to "low" or whatever.

[megavolt85]

1) remove check box "Enable SPI"
2) enable DMZ to xxx.xxx.xxx.98
3) reboot router

*DMZ activated only after reboot

[Xiden]

Also you can test with AFO, if you can start or join a game your DMZ should be working then.

[Gocha]

could be this one the reason for the dreamcast to not have a .98 IP?

Should I change the numbers so "98" is on the range?

[megavolt85]

Should I change the numbers so "98" is on the range?

In no way touch it

[Gocha]

Hahahaha ok ok, I thought that as the Dreamcast should be on an IP that is 98 but the range is from .100 to .199 it was probably the reason the dreampi was not putting the Dreamcast on .98

But hey, I have no idea of this kind of things.

Do you know what are those numbers?

[megavolt85]

This is the range of addresses that will be given to devices receiving IP automatically via DHCP

[Gocha]

This is the range of addresses that will be given to devices receiving IP automatically via DHCP

So how can the dreampi give an address that is out of range? the range is set to 100 - 199, but the dreampi is trying to get .98 (out of range) and subsecuently the DMZ is out of range. or I'm wrong with that?

Man, I really have no idea what I'm saying, but I'm a man on science and thats why I'm looking for an explanation, in no way im trying to offend anyone.

[megavolt85]

This is a range of dynamically issued addresses
Dreampi sets address statically

You better look at the WAN IP that the provider gave you and compare it to what will show the yandex.com to the request "my IP"