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Server 2008 and DHCP Help Please

Tags:
  • Routers
  • Internet Service Providers
  • Servers
  • Business Computing
  • DHCP
Last response: in Business Computing
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May 22, 2014 5:58:59 PM

Want to start out by saying I have some networking knowledge but not near enough. My experience with Server 2008 is not good but we don't have the money to hire an IT professional.

Originally we had a DSL router and our HP server running MS Server 2008. Our server is basically just a domain server. We have 5 workstations all running windows. The guy who installed our network (IT Pro) set-up DHCP on the server and it was giving out IP's to clients. When we moved, I had to get a new router because we went with a different ISP. It was my job to configure it and this is where all got screwed up. Currently, the Cisco router we have has DHCP enabled and is handling our IP addresses. All users can log into the domain, surf the internet, etc. no problem. However, I would like to get the network back the way it was originally with the Server handling the IP addresses.

None of the DHCP settings on the server have changed. The DHCP service is running currently. The router has the IP, Gateway, and DNS settings entered that the ISP gave me. If I turn off DHCP on the router than all outside connection dies. What I need to know is what in the world do I put in the router settings to have the server provide IP addresses? I'm at a loss.

More about : server 2008 dhcp

May 22, 2014 6:19:44 PM

It looks like you have two DHCP servers - a big NO-NO! Just disable DHCP on your router, and make sure DHCP on the server is enabled. Make sure DNS server configured in DHCP settings is actually alive (probably this is the same MS server).

When you disable DHCP on the router, "all outside connection dies". Make sure the gateway address your MS DHCP servier assigns is the internal address of your router!
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May 22, 2014 6:29:24 PM

Why do you want the Windows server to supply DHCP? Is it supplying any other network resources, such as acting as a DNS server or a router? I don't understand why you don't just let the router do it's thing.

However, if you insist of having the Windows Server handle DHCP, then it should be sufficient to set it up on the server and turn it off on the router. Just make sure that the Windows Server is handing out DHCP addresses in the same range that the router is on. For instance, if the router's NAT (internal) address is 192.168.1.1, then the Windows Server must hand out addresses in that range, i.e., in the range of 192.168.1.2 through 192.168.1.254, or some subset thereof. If the Server is handing out addresses in the range of 10.1.10.xxx, it isn't going to work.

Also, since the DHCP server hands out a PC's IP configuration in addition to the address, that is, it also hands out the Gateway (router) and DNS server, you must configure those on the Windows Server (DHCP server) to be the same that the router was previously handing out. So grab the router's DNS information before you turn off DHCP on the router and set that address up on the DHCP server. Also, in the Windows/DHCP server, make sure the Gateway (router) is the NAT address of the router, so that workstations know how to find the router, else they will never get to the Internet (probably what happened when you tried it before).

Once you have DHCP turned off in the router and turned on in the Windows server, boot up a workstation and go to its network port and look at it's IP configuration. See what address it has (it should be set to grab an IP address automatically), what Gateway address it has, and what DNS server it has. The workstation will get its Gateway address from the DHCP server (your Windows server), and it will grab its DNS server from the DHCP server.
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May 23, 2014 6:27:48 AM

Alabalcho said:
It looks like you have two DHCP servers - a big NO-NO! Just disable DHCP on your router, and make sure DHCP on the server is enabled. Make sure DNS server configured in DHCP settings is actually alive (probably this is the same MS server).

When you disable DHCP on the router, "all outside connection dies". Make sure the gateway address your MS DHCP servier assigns is the internal address of your router!


That is the strange part. The gateway address on the DHCP server is the internal address of the router. This is why I can't understand that when I turn off DHCP on the router the server does not hand out IP addresses. Even the server itself loses internet connection when I do this. Something just isn't right.

The reason I was trying to switch DHCP back to the server is because 1) that is the way it was configured originally, and 2) I'm trying to get a newly installed Win8 client hooked into the domain and it keeps telling me the AD DC for the domain cannot be contacted. I have tried a million different things (can ping the server, gateway, checked and double checked the computer/domain name) and nothing works. Weird because I just re-installed a Win7 client not long ago and it connected to the domain very easily. I ran a dns test via the command prompt and it failed so there are issues somewhere but I don't know what to do. Thought maybe if I could get things back to where it was originally it would fix this issue.
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May 23, 2014 6:40:49 AM

mbreslin1954 said:
Why do you want the Windows server to supply DHCP? Is it supplying any other network resources, such as acting as a DNS server or a router? I don't understand why you don't just let the router do it's thing.

However, if you insist of having the Windows Server handle DHCP, then it should be sufficient to set it up on the server and turn it off on the router. Just make sure that the Windows Server is handing out DHCP addresses in the same range that the router is on. For instance, if the router's NAT (internal) address is 192.168.1.1, then the Windows Server must hand out addresses in that range, i.e., in the range of 192.168.1.2 through 192.168.1.254, or some subset thereof. If the Server is handing out addresses in the range of 10.1.10.xxx, it isn't going to work.

Also, since the DHCP server hands out a PC's IP configuration in addition to the address, that is, it also hands out the Gateway (router) and DNS server, you must configure those on the Windows Server (DHCP server) to be the same that the router was previously handing out. So grab the router's DNS information before you turn off DHCP on the router and set that address up on the DHCP server. Also, in the Windows/DHCP server, make sure the Gateway (router) is the NAT address of the router, so that workstations know how to find the router, else they will never get to the Internet (probably what happened when you tried it before).

Once you have DHCP turned off in the router and turned on in the Windows server, boot up a workstation and go to its network port and look at it's IP configuration. See what address it has (it should be set to grab an IP address automatically), what Gateway address it has, and what DNS server it has. The workstation will get its Gateway address from the DHCP server (your Windows server), and it will grab its DNS server from the DHCP server.


Starting with the MS DHCP settings currently...

Under IPv4 these are listed:

Router (router ip address listed 192.168.1.1)
Time Server (server ip address is listed 192.168.1.2)
DNS Server (server ip address is listed 192.168.1.2)
DNS Name (full domain name listed)

Is the DNS address listed maybe the problem? It doesn't make sense that the DNS address is the internal server ip but what do I know. If it should be something else than what do I change it to?
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May 23, 2014 8:09:22 AM

So what is at the address 192.168.1.2? Is that your Windows Server? If so, you need to set up DNS on it, because that''s what everyone on your network will be going to in order to resolve web and computer names into IP addresses. If you don't' have DNS set up on the Windows server and don't want to, then set the Windows Server that is handing out DHCP addresses to give out the DNS server of your Internet provider.

EDIT: Think of DNS as the Internet's Yellow Pages. If your computers aren't pointing to a valid DNS server, then they won't be able to find anything, not Google, not your server, not each other. Whatever's at address 192.168.1.2 better be a valid DNS server or you're in trouble.
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May 23, 2014 11:58:10 AM

mbreslin1954 said:
So what is at the address 192.168.1.2? Is that your Windows Server? If so, you need to set up DNS on it, because that''s what everyone on your network will be going to in order to resolve web and computer names into IP addresses. If you don't' have DNS set up on the Windows server and don't want to, then set the Windows Server that is handing out DHCP addresses to give out the DNS server of your Internet provider.

EDIT: Think of DNS as the Internet's Yellow Pages. If your computers aren't pointing to a valid DNS server, then they won't be able to find anything, not Google, not your server, not each other. Whatever's at address 192.168.1.2 better be a valid DNS server or you're in trouble.


Yes. 192.168.1.2 is our Windows Server. DNS was setup on the Server originally and none of the configurations have been changed. If I go into the DNS Manager it has the zones and ip addresses all listed. Should all be good because the configurations on the server have never been messed with. Router is only thing that was changed as far as I know.

However, I did run a DNS test via command prompt on the server (I can't remember which test and what command was used) and the testing failed the initial and pretty much all the other ones.

Is there any information I can provide at this point?
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May 23, 2014 1:37:32 PM

OK, it doesn't necessarily mean anything that the DNS settings on your Windows server haven't changed, because your Internet provider has changed. Your Windows Server DNS is dependent on getting its information from your router, and your router has changed: Different Internet provider, different DNS feeding your Windows server.

Make sure that your Windows server DNS configuration is set to get its DNS from your router, and check that your router is getting its DNS setting from your provider (it probably is if the Internet works when connected to the router).

EDIT: I'm not a DNS expert, I just kind of install it on Windows server and it seems to take care of itself. If you can't get it working, just remove the role, reboot, then add the role again. That should take care of it.
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May 23, 2014 3:04:28 PM

mbreslin1954 said:
OK, it doesn't necessarily mean anything that the DNS settings on your Windows server haven't changed, because your Internet provider has changed. Your Windows Server DNS is dependent on getting its information from your router, and your router has changed: Different Internet provider, different DNS feeding your Windows server.

Make sure that your Windows server DNS configuration is set to get its DNS from your router, and check that your router is getting its DNS setting from your provider (it probably is if the Internet works when connected to the router).

EDIT: I'm not a DNS expert, I just kind of install it on Windows server and it seems to take care of itself. If you can't get it working, just remove the role, reboot, then add the role again. That should take care of it.


The problem is I don't really know what needs to happen for the MS DNS Server to get its DNS from the router. I know the router has the DNS addresses which the ISP gave me to use. Just don't know what the DNS is supposed to have because I have never set one up before nor do I have any training on it.
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May 23, 2014 4:51:46 PM

I would remove the DNS role and then add it again. Go through the configuration wizard for DNS. When that's done, open up the DNS applet on the server. Mine is later than yours (Server 2012 R2), but it should be similar.

In the left pane, under DNS, you should have an entry labeled with the server's name (at my home it's simply called "SERVER"). Right-mouse click on that and left-click on Properties.

Under the "Forwarders" tab, it should list the address of the router (in my server it just lists 192.168.1.1). Even though mine says, next to the address of my router "Attempting to resolve . . . ", then after a few seconds "Unable to resolve", when I Edit the entry it does resolve fine.

There is also a tab called "Interfaces". Make sure that lists the IP address of the network interface card (NIC) of your server. There should be a list of entries under "Root hints" also.

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