TheMotherload Posted July 2, 2014 Posted July 2, 2014 Hi everyone, I know this is my first post... Just a quick question for those who are sharp with DNS. Our school has 2 domain controllers, both have the DNS role installed and is running fine. On the NIC DNS settings for both DC's, the primary DNS is set for the 1st DC and the secondary DNS is set for the 2nd DC. It's been set like this for a number of years and I've had no problems however yesterday my colleague decided to change the secondary DNS on all the servers to an external DNS server. Is this the right thing to do? As far as I'm aware you would set the domain controllers to look at each other for DNS queries. Since the change there has been issues with people logging on etc. but I don't want to jump to conclusions here! Any insight is very much appreciated!
kmount Posted July 2, 2014 Posted July 2, 2014 Absolutely not, what your colleague has done will have a negative impact on your system. DNS Servers have a special section within their configuration called "Forwarders" which is where your ISP / External DNS servers can go, so they are only used if your DNS servers don't know the answer. Steer your colleague to the DNS best practices analyser - DNS: DNS servers on should include the loopback address, but not as the first entry 1
TheMotherload Posted July 2, 2014 Author Posted July 2, 2014 Thanks for that, so from what I gather it should be; 1st DC Preferred DNS : IP of 1st DC Alternative DNS : IP of 2nd DC 2nd DC Preferred DNS : IP of 1st DC Alternative DNS : IP of 2nd DC Or is the direct IP considered as the loopback and it needs to be the opposites? Cheers!
glennda Posted July 2, 2014 Posted July 2, 2014 What you have there is correct. Some people use 127.0.0.1 but i wouldnt recommend that 1
Sam_Brown Posted July 2, 2014 Posted July 2, 2014 What you have there is correct. Some people use 127.0.0.1 but i wouldnt recommend that Just curious. Why wouldn't you recommend using localhost?
glennda Posted July 3, 2014 Posted July 3, 2014 Just curious. Why wouldn't you recommend using localhost? Not 100% sure i read it somewhere years ago in a M$ article, I think it is just best practice not too but it is quite a topic of conversation with various people thinking different things (even Microsoft Engineers!) 2K8 - Best practice for setting the DNS server list on a DC/DNS server for an interface
kmount Posted July 3, 2014 Posted July 3, 2014 Just curious. Why wouldn't you recommend using localhost? Have a look at the best practices analyzer link I posted above, it explains why if you set it as a primary bad things /could/ happen.
TheMotherload Posted July 14, 2014 Author Posted July 14, 2014 Me again, We have experienced some problems with my network after my original posts... here is what I've done; I have reverted the changed DNS settings on all of the servers back to the originals but I still seem to be getting some problems... I have cleared the DNS Server cache and set GPO to clear cache on all of the client computers but the issues still persist. If I do an ipconfig /all on my computer it will still display the external DNS server. this is after a manual flushdns and renew of the ip address. I'm not sure how to troubleshoot from here any suggestions?
glennda Posted July 14, 2014 Posted July 14, 2014 Me again, We have experienced some problems with my network after my original posts... here is what I've done; I have reverted the changed DNS settings on all of the servers back to the originals but I still seem to be getting some problems... I have cleared the DNS Server cache and set GPO to clear cache on all of the client computers but the issues still persist. If I do an ipconfig /all on my computer it will still display the external DNS server. this is after a manual flushdns and renew of the ip address. I'm not sure how to troubleshoot from here any suggestions? On your local machine or on the domain controller itself?
TheMotherload Posted July 14, 2014 Author Posted July 14, 2014 On your local machine or on the domain controller itself? Local PCs, the DCs reflect the DNS servers fine.
Oaktech Posted July 14, 2014 Posted July 14, 2014 (edited) Me again, We have experienced some problems with my network after my original posts... here is what I've done; I have reverted the changed DNS settings on all of the servers back to the originals but I still seem to be getting some problems... I have cleared the DNS Server cache and set GPO to clear cache on all of the client computers but the issues still persist. If I do an ipconfig /all on my computer it will still display the external DNS server. this is after a manual flushdns and renew of the ip address. I'm not sure how to troubleshoot from here any suggestions? Someone did something like that here a while ago... It took best part of a week to iron out all the DNS issues as machines didn't flush for ages. We enede up doing manual flush and check whenever an issue cropped up. Hold the phone... Has he set the DNS servers in DHCP options too? Edited July 14, 2014 by Oaktech
TheMotherload Posted July 14, 2014 Author Posted July 14, 2014 (edited) Someone did something like that here a while ago... It took best part of a week to iron out all the DNS issues as machines didn't flush for ages. We enede up doing manual flush and check whenever an issue cropped up. That's what I've been doing, it was bad last week and not so bad now but I don't why my client PC, for example is still showing the old external DNS in its list. Edited July 14, 2014 by TheMotherload
Oaktech Posted July 14, 2014 Posted July 14, 2014 That's what I've been doing it was bad last week and no so bad now but I don't why my client PC for example is still showing the old external dns in its list. I think it's in DHCP scope options... 1
Oaktech Posted July 14, 2014 Posted July 14, 2014 There is an issue with attachments... Right click open in new tab should let you view it.
glennda Posted July 14, 2014 Posted July 14, 2014 under ipconfig /all does it say the DHCP server is the servers IP address? If so login go to Administrative Tools/DHCP and set the DHCP options for DNS server to the Domain controllers IP's. 1
TheMotherload Posted July 14, 2014 Author Posted July 14, 2014 I think it's in DHCP scope options...[ATTACH=CONFIG]25618[/ATTACH] Thanks, I've found the culprit. The external DNS is set here... I'm at a loss for words right now.
smithson83 Posted July 14, 2014 Posted July 14, 2014 (edited) Sorry to hijack, but shouldn't both DCs DNS be set as Primary: Own IP Address Alternate: A.N.Other DNS Server IP Address rather than both pointing to DC1 as primary and DC2 as Alternate? Edited July 14, 2014 by smithson83
Boredguy Posted July 14, 2014 Posted July 14, 2014 Sorry to hijack, but shouldn't both DCs DNS be set as Primary: Own IP Address Alternate: A.N.Other DNS Server IP Address rather than both pointing to DC1 as primary and DC2 as Alternate? Nope, that was what caused the issue in the OP to begin with Only time it would not have another DC as a secondary address is if you only have 1 DC
smithson83 Posted July 14, 2014 Posted July 14, 2014 I ment another local dc eg DC2 ie Use yourself, unless something is wrong, then use the other dc on the network So DC1 would be; Primary: IP of DC1 Alternate: IP of DC2 and DC2 would be; Primary: IP of DC2 Alternate: IP of DC1
Boredguy Posted July 14, 2014 Posted July 14, 2014 Yes, which was post 3 in the thread DC's always reference themselves, then the IP of another DC where possible.
smithson83 Posted July 14, 2014 Posted July 14, 2014 Post #3 was why I asked, it says both DC1 and DC2 should have IP of DC1 as primary and IP of DC2 as secondary, should it not be reversed on DC2
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