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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.

Any ideas?

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migrated from serverfault.com Aug 2 '13 at 4:35

This question came from our site for professional system and network administrators.

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You have to make a decision whether you want the two routers handling the same LAN or making two LANs. You keep splitting the difference, and that won't work. If you want them to be the same LAN, you must connect them LAN-to-LAN, not LAN-to-WAN. And if you want them to be different LANs, you have to give them addresses in different subnets. –  David Schwartz Aug 2 '13 at 5:50
    
You're right, I see that now and now understand why. So I've went the route to make them separate networks but am running into the issue I described in a comment below techie007's answer below –  codemann8 Aug 2 '13 at 21:39

2 Answers 2

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Firewalls/Routers have trouble routing to the same subnet; I'm surprised this setup ever worked.

So if 192.168.2.x/24 (255.255.255.0) is on both the LAN and WAN sides of a router, it won't be able to figure out how to route traffic since there isn't a route between them needed, as it's the same (sub)network. The router expects them to be different networks.

You need to think of it (and reconfigure it) as three networks. The Internet, the one between the routers, and then the internal LAN.

The two you own should be different networks (say 192.168.1.x and 192.168.2.x). There's no reason for them to be on the same IP range to be able to communicate (that's what the routers are for).

To forward in from the Internet (say port 80), you'd forward it in the first router targeting the second router's WAN port, and then forward it in the 2nd router to the target server's IP.

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I've actually started to resort to this. I'm now in the process of converting my second network to 10.0.0.x while leaving the main router alone. I seem to have internet coming thru now, but I'm not able to connect to these from the outside. –  codemann8 Aug 2 '13 at 5:44
    
I now have my second router statically WAN set to 192.168.2.2 and SM 255.255.255.0 (as defined in main router) and gateway *.1. I then have my port forwarding set on my main router to forward port 3389 (the Windows RDP port, for remote connections) to 192.168.2.2:3389 and then also on my second router I am forwarding port 3389 to 10.0.0.202 (the computer I want to connect to, and it shows up in the client list so I know it's valid). But, however, it does not seem to work. What's odd is that 192.168.2.2 does NOT show in the client list of the main router. Should it? –  codemann8 Aug 2 '13 at 5:45

another simpler solution, since you have already disabled DHCP on the dlink, is to use a LAN port on the dlink to connect to a LAN port on your "main router"

This way, you are just using the built in switch of the dlink and not bothering with its routing capablilities.

This way you would have

  • Main router with
    • IP 192.168.0.1
    • subnet 255.255.255.0
    • WiFi enabled
    • DHCP enabled with address pool *.20 - *.100
  • 2nd router (dlink model) with
    • IP 192.168.0.2
    • subnet 255.255.255.0
    • DHCP disabled
    • WAN ip in some other subnet
    • default gateway would not be used

Everything (except the dlink) would have a default gateway of 192.168.0.1 and subnet of 255.255.255.0

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