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Multi Homed and DNS fails (despirate!!)

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9 replies

by david__

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My new 2000 Server has Exchange installed and a Webpage. I had the same confiugration on a server that is in the process of dieing. I have two nics, one for LAN and one for WAN (Exchange and Webpage). The are on seperate routers. Both are on the same DSL provider, but seperate IPs and routers (both static). The problem is that if I have the WAN card enabled, then DNS fails. It is setup the same way the old server is (new local IPs of course). The LAN card is (for example)192.168.100.10, 255.255.255.0, Gateway is 192.168.100.1 and DNS is 127.0.0.1 (it is its own DNS server). The WAN is 192.168.200.10, 255.255.255.0, Gateway 192.168.200.1, DNS is ISP provided servers. Register with DNS server is not checked.
In DNS settings I only have it set to listen on the LAN IP.
Clues???

Thanks,
David

9 replies

by cg it

Humm 2 routers? one connected to the WAN NIC which I get but wheres the second one connect to and if its the LAN NIC whats the router for? I mean why route packets from clients to a server that would normally coexist on the same LAN?

anyways if you remove the LAN router from the mix and just take the LAN NIC cable and connect it to a big switch configure the LAN NIC as it already is except do the following. remove the gateway address from the LAN card settings. Add in the 192.168.100.10 IP address of the NIC into the DNS settings [the priority is first line 192.168.100.1 second line the loopback 127.0.0.1 [DNS will work without the loopback addres there]

DNS IS the LAN NIC. That is DNSs address so it must be listed in the DNS settings for LAN clients [also in DHCP settings if LAN clients use DHCP to obtain DNS info. Your WAN NIC looks correctly configured. Now clients gateway address is the WAN NICs IP address.

by cg it

oops damnit correction:: the gateway address for LAN clients is the WAN Router IP address [which the WAN NIC attaches to].

by david__

Sorry for not being clear, like I said, Im a little fried right now. The LAN nic is connected to a switch, there is a seperate router for the LAN to access the internet, the LAN internet access does not go through the server, just DNS requests.
The clients have nothing to do witht the question, it is the DNS that fails on the server. When you open DNS and go to properties and then to Monitor and click test, both test fail.
Putting the IP instead of the loopback did not help.
If the WAN nic is enabled the server can not even find itself, it seems, both DNS tests fail.

Thanks for the input.
David

by cg it

once again 2 NICs 1 WAN 1 LAN. WAN is configured as the external interface with an IP address which fits within the routers IP address and subnet mask range. the LAN NIC can be any Class C address BUT that which you've designated as the WAN segment. If your routers IP is 192.168.2.1 with a subnet mask 255.255.255.0 the WAN NIC is 192.168.2. 3,4,5,6-253 subnet mask 255.255.255.0. Default gateway 192.168.2.1 [the router]. The LAN NIC then would be configured as a different segment. 192.168.24.1 subnet mask 255.255.255.0 [ Class C ] DNS is 192.168.24.1 [itself][the domain controller] DNS records would reflect that. "Host" "A record" 192.168.24.1 A LAN query against that record would say "yep" >domain controller name> = 192.168.24.1. If there isn't name to IP resolution then the record may be the problem.

by david__

The network settings are not the problem. I have narrowed it down to two possibilities:
1. DNS is just fried. I have tried to uninstall and reinstall it, but same thing.
2. DNS is trying to use the WAN card IP to attempt DNS resolution for the LAN instead of the LAN card IP.

Please keep in mind that the server can even find itself. In the DNS console all looks normal, IP and name listing for A records are all right. But exchange will not start because it cant find a DNS server.

If I uninstall DNS and just use the existing DNS server all works fine, but I really would like to have two DNS server for the network.

David

by curlergirl

I think your problem is not DNS itself but that you have two default gateways on your multi-homed server. What is the 192.168.100.1 host - is it a router, another server or what? I really don't quite understand why you are using two separate subnets, since none of your IP addresses are public. If the two separate NICs are connected to two separate routers, both with public IPs for some reason, and you need to use both gateways, you are going to have to do some static routing on this machine to make it work. Normally, the LAN card should have NO default gateway defined at all. The default gateway on the WAN card should be your router, just like the other clients on the LAN. Also, if DNS is being provided by your ISP, you should be sure you have your internal DNS server set to forward to the ISP's DNS servers; then all your internal machines, and your router, should be set to use the internal DNS servers, which will forward any non-internal requests to the ISP's DNS servers.

If this seems confusing, it's because I'm a little confused about why the configuration is so complicated. But if you have questions about my comments, please feel free to email me directly. Hope this helps!

by curlergirl

Also forgot to add that rather than using 127.0.0.1 (loopback) as the DNS server setting on your server, use its actual private IP address (i.e., 192.168.100.10, I think it was).

by david__

I have solved the problem on my own. I ended up totaly removing and adding back DNS for the entire domian, and that fixed it.
Thanks anyway.

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