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DNS resolution issues

Posted on 2008-10-19
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Last Modified: 2012-05-05
After rebuilding my Exchange server on a different box with the same IP but a different name, I am experiencing DNS issues. Randomly during the day we loose connectivity to the Exchange server. The nslookup resolves the correct IP however I am unable to ping the server name. With no intervention from the IT department the server comes back on line; pings are successful. Any idea why?
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Question by:rbrindisi
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17 Comments
 
LVL 17

Expert Comment

by:JohnGerhardt
ID: 22752757
Do you have more than one DNS server in the domain.. Maybe the records arent synced correctly..
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Author Comment

by:rbrindisi
ID: 22752764
Yes I do, how can I check?
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LVL 17

Expert Comment

by:JohnGerhardt
ID: 22752783
Two ways...
nslookup from a client machine and then force it to look and the server by typing
server nameservername.domain.lcoal
then query for the mails server
Else
look on the severs them selves..
Start =>Run => dnsmgmt.msc
Search for the A records (check MX records as well) for the mail servers on each of the DNS servers...

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LVL 3

Expert Comment

by:leonjs
ID: 22752946
Are you unable to ping the server by name when you loose connectivity or all the time ?
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LVL 18

Expert Comment

by:Andrej Pirman
ID: 22753890
Go to your DNS mmc and browse down into reverse lookup zones. Sort zones by name and see, if there are more IP's listed for your exchange server. You may freely delete all wrong reverse PTR records, which point to wrong exchange IP.

Also do the same check in forward zones for Exchange server.

And not last - check, if you do NOT have by accident some other foreign DNS server set in DHCP for clients, or in tcp/ip properties on NIC on DC or Exchange - only local AD-integrated DNS should be there!
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LVL 39

Expert Comment

by:ChiefIT
ID: 22753920
Either forwarders or you might be running SP1. SP1 has a bug in it that will flood even a single nic. If you are usig SP1, consider downloading and installing SP2. I can provide details if you wish.
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LVL 59

Expert Comment

by:Darius Ghassem
ID: 22754085
Another check I would do is sort by IP addresses within the DNS console to see if you have more then one record listed for this IP. If you do then you should remove the old record.
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Author Comment

by:rbrindisi
ID: 22757968
Ok some more info:

On DNS1:
Nslookup on DNS1 server name resolves:
10.x.x.1 and 8.x.x.1 (OK)

Nslookup on DNS2 Email server name resolves:
10.x.x.28 and 8.x.x.3 (OK)

Ping email server name:
10.x.x.28 --- OK

On DNS2:(email server)
Nslookup  on email server name cant find server name.

Nslookup on DNS1 server name same as above.

Ping DNS1 server name 10.x.x.1 (OK)

Ping DNS2 server name 8.x.x.3 (Not Good!! Should be be 10.x.x.28)
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LVL 59

Expert Comment

by:Darius Ghassem
ID: 22758068
Have you looked in DNS to see if you have a different IP address listed on DNS2?
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Author Comment

by:rbrindisi
ID: 22758745
DNS2(email2) has 2 NICs a 10.x.x.28 and 8.x.x3 for some reason when I ping the DNS2 server name on the DNS2 it only resolves the 8.x.x.3, not the 10.x.x.28.
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LVL 59

Expert Comment

by:Darius Ghassem
ID: 22759122
Is the 8.x.x.3 a public address? You should only have one name listed for an IP address. For an example Server2 should only resolve to one address 10.x.x.28. You can go to the Local Area Connection then go to the properties of Internet Protocol click Advance then go to DNS tab uncheck register this with DNS.
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LVL 18

Expert Comment

by:Andrej Pirman
ID: 22761949
1.) As Dariusq already said, if 8.x.x.x is public address, and 10.x.x.x is LAN IP range, you obviously have DNS configuration conflict! You should not mix public and LAN IP subnets.
2.) As Dariusq said, you can un-register specific NIC card from your DNS, and in advance you may configure DNS to serve only on specific IP or NIC under Properties of DNS server. You should do so.
3.) Do not just ping and nslookup. Instead go to your DNS server and see actual zones, how are they configured. By-the-book config should look like this:
- your internal DNS should be bind only to internal IP
- your internal DNS server should have only internal DNS listed in TCP/IP properties of NIC adapter
- your internal DNS should be configured to use forwarders for all queries, it cannot reslove itself
- exchange should use local DNS only
4.) I think the main problem is on your DNS2 - either it has some public DNS under Properties of TCP/IP for NIc adapter, or it has DNS server bind to wrong (public) IP
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Author Comment

by:rbrindisi
ID: 22769237
Sorry for the delay

Thank you for your patience and expertise. I have been involved in other issues and will return to this by mid week.
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Author Comment

by:rbrindisi
ID: 22866491
So sorry for the delay, unexpected business travel.

As it turns out there was a flakey NIC, no DNS issue. I replaced the NICK and all is well. I am unsure on how to handle the points regarding this question. Can someone please advise.

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LVL 59

Accepted Solution

by:
Darius Ghassem earned 250 total points
ID: 22867204
Look over this link. Did you remove the external DNS server from your NIC?

http://www.experts-exchange.com/OS/Microsoft_Operating_Systems/Windows/ME/Q_22783204.html
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LVL 18

Assisted Solution

by:Andrej Pirman
Andrej Pirman earned 250 total points
ID: 22876729
Regarding points awarding:

since you resolved the issue actually yourself and sollution was not mentioned in any of expert's answers, you may select your answer as sollution and points will be discarded (and returned back to your pool).

But if you want to award some of experts here for trying to help you, you may choose link "Accept Multiple sollutions" under ANY of given answers, and then manually split 500 points among those experts, which you think contributed best.

Choice is up to you :)
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Author Closing Comment

by:rbrindisi
ID: 31507612
So sorry for my long delay. I decided to split the points equally. Even though my problem was not a DNS issue, your prompt responses were greatly appreciated.
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