I just had an incident where a router died and I went to replace it and entered what I thought were the same settings as the original, but I just can't seem to get this to work. Let me start by describing my network as it was in working order.
My setup is my ISP is connected to my modem, and the modem is connected to the main router (a Belkin, on WAN port of course), and my main router connected to my second (a DLink, WAN port connected to main LAN port 1). I have wireless disabled on the second but enabled on the first. The main router is 192.168.2.1 and DHCP enabled from *.20 - *.100 and various home devices connect to this wirelessly (phone, computer, XBOX, etc). My second router was 192.168.2.2 and DHCP disabled. My intention was that the second router be a separate network and that any devices connected to this one needed to be manually set up (as I have a couple servers connected that must have static IPs). The devices connected to the second have IPs of *.200 and above. *.200 is also my DNS and domain controller, also all devices connected here exist in my domain. Also, I have port forwarding set up on the main router to point to servers/ports of computers connected to the second network as I do a bit of remote work with these, and my main router only allows me to port forward on the last number of the IP address. I'm not sure what other information I should include.
I recently just had an incident where my second router died, and so I went out and bought another router, a cheap one as I don't need wireless and I also don't require gigabit. The router that died was a DLink and I bought a Belkin to replace it, mind that now I have two Belkin routers now (both default to the same address).
I plug everything physically exactly as before. And I go to configure the new router using one of the physically connected servers I have there. Belkin now has an automatic way of setting up the network settings, it seems it recognizes that 192.168.2.1 is already in use so it defaults to 10.0.0.1 and I have full internet access, but if I leave it this way I'm no longer able to port forward to anything on this router. So, I change the IP to my desired 192.168.2.2 and disable DHCP and such and I leave the WAN settings as Dynamic to allow the main router to take care of it. Now I don't have internet on the second network. I've also modified the WAN settings to a Static address of 192.168.2.2, that didn't work either. As far as DNS, I'm not much of a network guy but my understanding is that's really only for recognition of computer names vs. IPs. And so far I'm not trying to access things by name yet so those settings shouldn't matter, I've already been toggling between automatic and 192.168.2.200 for primary (my DNS server) and 192.168.2.1 for secondary (the main router). Still nothing.