DNS resolution issue

SuzenJ
SuzenJ used Ask the Experts™
on
Hi EE,
I've a DNS resolution issue as below and it's just happened recently.
My backup failed to connect to the NAS storage due to this issue.

When i nslookup nasb01.fish.com, I will get result:

Name:    nasb01.fish.com
Addresses:  57.x.x.x, 57.y.y.y, 57.z.z.z, 57.28.222.123

However, from the DNS server i couldn't find any host A record for nasb01.fish.com.

Tried to nslookup the IP, and the IP resolves as follow:
57.x.x.x = nas111.fish.com
57.y.y.y = nas132.fish.com
 57.z.z.z = nas27.fish.com
57.28.222.123 = nasb01.something.fish.com

Can you guide me how to troubleshoot this issue?
The correct resolution is nasb01.fish.com = nasb01.something.fish.com = 57.28.222.123
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Top Expert 2015

Commented:
Have you tried flushing the dns on the computer you tried to backup?  Also, you can also explicitly map the hostnames ( nasb01.fish.com and nasb01.something.fish.com) to IP addresses (57.28.222.123) on the computer you tried to backup.

Here is more info for Windows 7: http://helpdeskgeek.com/windows-7/windows-7-hosts-file/

It's different for MAC, Linux, etc.

Author

Commented:
My backup server is running on windows 2003.
Before I open this case, I've updated the hosts file to map the IP addresses to the host names.
However, I need to resolve the DNS issue.

Wondering why i'm able to resolve the hostname nasb01.fish.com to these IP addresses but the host A record is not found from DNS server. Is there anything I need to check from SAN storage side?
Top Expert 2015

Commented:
It sounds like a round-robin DNS scenarios without the need of the hosts entry in a DNS.

http://serverfault.com/questions/69836/point-multiple-ip-addresses-to-a-single-host-name

Do you see in the dns forward lookup table entries for nasb01.fish.com
to these addresses:  57.x.x.x, 57.y.y.y, 57.z.z.z, 57.28.222.123?
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Author

Commented:
Hi Wayne88,
I've tried to flush the dns but still the same.
No dns forward lookup table entries found for nasb01.fish.com from my DNS server
I understand about round robin dns. I've tried to ping the nasb01.fish.com few times and from few servers and received below results:

C:\>ping nasb01.fish.com

Pinging  nasb01.fish.com [57.x.x.x] with 32 bytes of data:

Request timed out.
Request timed out.
Request timed out.
Request timed out.

Ping statistics for 57.x.x.x:
    Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),
Mark BillExchange, AD, SQL, VMware, HPE, 3PAR, FUD, Anti MS Tekhnet, Pro EE, #1

Commented:
im confused here, ok if your saying nasb01.fish.com
is your active directory name fish.local ?

is this nas local or remote from the 2003 backup server?
once your active directory domain is configured fine for DNS i.e. using its own DNS servers IP addresses only you could just connect to this hostname by ip? you could also just create a forward lookup zone in AD?
DrDave242Principal Support Engineer

Commented:
How many internal DNS servers do you have? Does each one have a copy of the fish.com forward lookup zone? Within that zone, is there an A or CNAME record for nasb01?

You also mentioned nasb01.something.fish.com. What is something? Is it a child domain within the fish.com domain? Is there a corresponding something.fish.dom forward lookup zone on your DNS servers, or a folder named something within the fish.com zone?

Sorry, I know that's a lot of questions. I'm just trying to get a good idea of how everything's arranged.

Author

Commented:
Hi Mark/DrDave242,

I've no visibility to the NAS storage. Backup server connects to it remotely.
2 internal DNS servers (AD-integrated). Both have the same records.

From something.fish.com forward lookup zones, we only have below host A records
nasb01 = 57.28.222.123

From fish.com forward lookup zones, we only have below host A  records:
nas111 = 57.x.x.x
nas132 = 57.y.y.y
nas27 =  57.z.z.z
nasb011 = 57.28.222.123

From fish.com reverse lookup zones, we have below records:
57.x.x.x = nas111.fish.com
57.y.y.y = nas132.fish.com
 57.z.z.z = nas27.fish.com
57.28.222.123 = nasb01.something.fish.com
57.28.222.123 = nasb011..fish.com

Please find below nslookup results from DNS server:
C:\Documents and Settings\xxxx>nslookup
Default Server:  dc05.something.fish.com
Address:  x.x.x.x

> nasb01
Server:  dc05.something.fish.com
Address:  x.x.x.x

Name:    nasb01.something.fish.com
Address:   57.28.222.123

> nasb01.something.fish.com
Server:  dc05.something.fish.com
Address:  x.x.x.x

Name:    nasb01.something.fish.com
Address:  57.28.222.123

> nasb01.fish.com
Server:  dc05.something.fish.com
Address:  x.x.x.x

Name:    nasb01.fish.com
Addresses:  57.x.x.x, 57.y.y.y, 57.z.z.z, 57.28.222.123
DrDave242Principal Support Engineer

Commented:
From fish.com forward lookup zones, we only have below host A  records:
...
nasb011 = 57.28.222.123


Is that a typo (should it say nasb01), or is that the actual name on the record? If that's really how the name appears, do you know why that record is named nasb011 and not nasb01, since it refers to the same IP address? Any chance the record itself has a typo in the name?

Author

Commented:
Hi DrDave242,
This is my concern as well..From the fish.com forward lookup zones, there is no nasb01 record. I only managed to find nasb011 = 57.28.222.123.  I've asked my colleagues to double check as well.

As far as I know there is no changes on the DNS record, but the interesting part is I'm able to nslookup the nasb01.fish.com eventhough the record doesn't exists. Still scratching my head to resolve this issue.
DrDave242Principal Support Engineer

Commented:
I don't understand those nslookup results. Obviously I can't see your DNS structure, but I don't get why it's returning four addresses for nasb01.fish.com when there's no record for it at all. That doesn't make sense. Changing the nasb011 record to nasb01 should fix the problem, since that will (should?) be the only address returned for that name.

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