Maintaining internal and external DNS

Posted on 2012-12-28
Last Modified: 2013-01-08
Feels weird to be on this side of the question.  

I have users who need to connect to a vendor via both External and internal IP addresses.  Let me explain.

Lets say that your client is microsoft (not really).  I need to have the user resolve an ip address for but this address is a private address (not in Microsoft's external DNS) that needs to go through a specific VPN connection.  The user ALSO needs to connect to via the internet.  

I have the routing correct.  The way we have been doing this in the past is to user local "host" files.  We are getting too big to manage these files.  I need to get them on DNS and manage them from there.

I tried added a primary zone with a forwarder to (google external DNS).  The address works but I then can not resolve

I am running DNS on Windows 2008 R2 domain controllers.

Thanks for the help.

Question by:mav7469
LVL 29

Accepted Solution

becraig earned 500 total points
ID: 38727674
Though I don't like the approach you are taking and would prefer to stay with host files to avoid issues with name resolution down the road, here is an idea.

Don't create a zone, rather create a zone then create an empty A record to point to the address you need.

All other requests will be resolved by public dns.

Author Comment

ID: 38727696
The only issue I can see with this idea is that we are talking about dozens of clients with dozens of addresses each.  Will that overload the DNS server?  Is there a limit as too the number of zones?

LVL 40

Expert Comment

ID: 38727806
I'm having trouble picturing your situation.  In your original question you mention one site that needs to resolve to an internal IP and one that needs to resolve to an external IP.  Then in your last post you mention dozens of clients with dozens of addresses.  Can you describe that better?  What is the number of addresses that need to resolve to an internal IP vs. the number that should be resolved by public records?  And are these all for the same domain or for different ones.

The solution that becraig proposed is the route to take if you have one site that needs to resolve to a different IP than what is present in public DNS records.

A flip of that, if you have just one site/host that needs to be resolved by public records, while the rest are resolved by internal records, is also possible.  To do this, you would have a zone for "", with all the internal A records, then for a record you want to resolve by external records create a delegation that points at the SOA for the domain in public DNS.  Let me know if you need more detail or you can find instructions here:
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LVL 29

Expert Comment

ID: 38727866
I don't follow

The only issue I can see with this idea is that we are talking about dozens of clients with dozens of addresses each.  Will that overload the DNS server?  Is there a limit as too the number of zones?

Are you saying you expect to have personalized host records for multiple public dns sites ?

If you don't mind me asking what is the aim here ?
If this is for traffic management you may want to look into a traffic management solution or an ISA/TMG server.

I cannot see a scenario where you would need to have a host record on your dns server for a hundred or more public zones (namespaces you do not own)

Author Comment

ID: 38728241
The only issue I can see with this idea is that we are talking about dozens of clients with dozens of addresses each.  Will that overload the DNS server?  Is there a limit as too the number of zones?

I was speaking to the answer given to create a zone for each host file entry.

Right now, we have 105 different entries in our host files that we have to manage on over 400 computers.  These host files can change at the whim of our client (they change a process to a different server for example).  Becasue we can not manage the host files via script, I want to move them to DNS so I only have to touch one place to make changes instead of 400 different computers.
LVL 29

Expert Comment

ID: 38729840
Both scenarios are viable and if your dns server is only available on your intranet (via vpn or direct access)  You can also script one host file and propagate to all the clients every time a change is made (Since you would have to be notified in the case of DNS as well).

The choice is your but the solutions offered above would work, a little more visibility into:
Approximately how many public domains are you spoofing ?
Are the clients only using your dns servers for name resolution ?
Is your dns server available to your clients on the internet or only on the intranet ?
would help to create a better view of what is required.
LVL 26

Expert Comment

ID: 38733214
It sounds like your client has identical public and private DNS domain names.  That's never a good idea, although I think this is the first time I've considered the administrative nightmare that it can cause for a partner in an extranet scenario.  105 entries in your hosts files?  That's insane.

It seems likely that most of the addresses you'll need to resolve are private addresses.  If that's the case, you can use either conditional forwarders or a stub zone to send those queries to your partner's DNS servers.  Then you don't have to update anything when they make changes internally, and you can create forward lookup zones on your DNS servers (as has already been mentioned) for the public addresses, which aren't likely to change much.

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