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DNS Question

Posted on 2006-04-23
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Last Modified: 2010-03-19
We have just reconfigured our network and everything is working other than one thing.

When we try to browse some of our subdomains that live on internal servers, we get get to the new NetGear ADSL router.

Externally this works fine. But internally it's not working. I think I need a static route of some sort but am not really sure.

An example is our intranet.

intranet.company.com

Externally it works fine, internally it doesn't.

We have our own DNS server internally so intranet.company.com points to our fixed IP from our IP, ie a real IP.

So what I think is happening is when I browse it internally, it's trying to send it out and not coming back in.

Any assistance would be appreciated.
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Question by:Plucka
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13 Comments
 
LVL 15

Expert Comment

by:nprignano
ID: 16522800
if intranet is hosted on your internal servers, you should have a DNS record for intranet.yourcompany.com pointing to the internal IP address of the webserver, not your public IP.  Also, make sure your DNS server is set as the primary DNS for your internal PCs, either static or through DHCP.

nprignano
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Author Comment

by:Plucka
ID: 16522844
Yes,

But the problem is that this DNS server is also one of our real DNS servers, ie NS2

So it needs to have the real IP.
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Expert Comment

by:nprignano
ID: 16522877
but you said this was an internal DNS.  the internal DNS should be the primary DNS for all the internal PCs, with either a host (A) record pointing to the internal IP of the server hosting the intranet, or an alias (CNAME) record poitning to the server name inside your domain.  If you do not have this setup this way, your PCs will not be able to talk amongst the network based on computer name - can you reach the intranet by entering the IP into the browser?  this is a clear validation of my statement.


nprignano
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Author Comment

by:Plucka
ID: 16522890
It is internal to our office, and serves for both internal and real domains.
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LVL 19

Expert Comment

by:CoccoBill
ID: 16522942
Is your internal naming scheme the same as your external namespace, that is, is your internal DNS zone also company.com? If so, you've just run into one of the reasons why its generally not a good idea, you will get problems when trying to distinguish between internal and external names. In that case you can either use a quick fix and create a separate CNAME as nprignano suggests, such as intra.company.com, and point that to the intranet server's internal IP. The proper way to fix this and to avoid other problems in the future is, unfortunately, to change your internal DNS naming to something resembling FQDN such as company.local, which would most likely require a complete domain restructure/reinstallation.
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Expert Comment

by:Nopius
ID: 16522951
Use internal IP of your DNS server as primary DNS.
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Expert Comment

by:The--Captain
ID: 16523003
The problem is that the when you internal clients send outbound packets to the webserver's external IP, the firewall is translating the destination address (the public IP of your webserver) to the private IP of your webserver, and then your webserver tries to respond directly to the local client using it's internal address (because the packet has a source IP within the internal subnet), but the internal client is expecting packets from the webserver's external IP address, and ignores the packets from the webserver's internal address.  You can fix this using DNS hacks (split-dns being most common), or by just creating a different internal subnet for the webserver (if the firewall will let you do that), or by getting a decent firewall that lets you translate individual source addresses (SNAT) as well as destination addresses (DNAT).

Cheers,
-Jon

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LVL 19

Expert Comment

by:CoccoBill
ID: 16523056
Going through the other thread, here's more specific instructions:

Create a Host (A) record in your internal DNS forward lookup zone (company.com?) with a different name than the external name of your intranet, such as "intra" instead of "intranet". Point this A record to the internal IP address of the intranet server. Instruct the users to use intra.company.com to access the intranet internally and intranet.company.com when connecting remotely.
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Author Comment

by:Plucka
ID: 16523594
That won't work,

There are lots of internal stuff not just the intranet that this is a problem for.

I think there is probably a simple solution. At the moment, I think this might be having two internal DNS servers.

I'll see if any more great ideas arrise.
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Expert Comment

by:CoccoBill
ID: 16523841
Again, is your internal naming scheme the same as your external namespace? That is, is your AD's DNS name company.com and your external website/domain also company.com? If that's the case the only way to avoid conflicts and manual administration of DNS records is to change one or the other. The proper way is to change the internal naming to something that does not and will not conflict with the public namespace, such as company.local. This, however, is typically a monumental task and might require a complete domain restructure. I'm afraid there's no easy way out.

Here's some additional reading:
http://support.microsoft.com/?id=254680
http://technet2.microsoft.com/WindowsServer/en/Library/7f6df44c-06c3-4b92-ba32-63d895a7924b1033.mspx
http://www.petri.co.il/w2k_domain_rename.htm
http://www.petri.co.il/windows_2003_domain_rename.htm
http://technet2.microsoft.com/WindowsServer/en/Library/4d0c3b6e-e6f5-4ab3-9d81-106ae3a715491033.mspx
http://www.msexchange.org/tutorials/Domain-Rename.html
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LVL 19

Expert Comment

by:BLipman
ID: 16530510
Um, you really should have separate internal and external DNS servers.  Set your internal DNS servers to the internal addresses and foreward to your external ones.  You are fighting how DNS is designed to run.  
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Accepted Solution

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The--Captain earned 0 total points
ID: 16532814
Over 24 hours have passed since my initial objection, and Plucka has apparently chosen to ignore my request.

As such, I am closing this question and referring all responders to this question to join the thread at:

http://www.experts-exchange.com/Networking/Q_21824447.html

Cheers,
-Jon
EE Networking PE
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Author Comment

by:Plucka
ID: 16532958
Well done, you should be proud.

You are well aware  I did respond in the other question.
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