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Odd Dns Problem , Ip = Ok , Fqdn ! Ok


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8 replies to this topic

#1 1dmf

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Posted 27 March 2009 - 05:58 AM

Hi,

I'm rather puzzled....

I am unable to ping / connect to our webserver via its FQDN which we have a VPN tunnel connection to.

If I ping the respective IP I get a reply, If I nslookup the FQDN I get the correct IP resolution.

I've checked the server event viewer DNS log, no errors reported.

everything seems fine, I've looked in the DNS Active Directory and there is the correct Host(A) record.

I can only get a response if the IP is used but not the FQDN

What's really odd, is 10-15mins later it's working again and nothing has been done to potentially 'fix' it.

I also spoke with the missus who manages 5 servers and @ 70 users across 2 office locations and she experiences on occassion exactly the same phenomenon.

We do use the same ISP, but this is an internal AD DNS issue isn't it?

Any ideas as to what is going on?

Thanks,
1DMF

Edited by Jill, 27 March 2009 - 08:14 AM.


#2 1dmf

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Posted 30 March 2009 - 07:10 AM

No one got any ideas? Not even you Randy?

QUOTE
This post has been edited by Jill: Mar 27 2009, 02:14 PM
really, what I do wrong dntknw.gif

#3 Randy

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Posted 30 March 2009 - 09:12 AM

It's hard to say. It could be a local ISP problem, or it could be something with the DNS of the domain itself. Or it could be a setting in your hosts file for that matter.

If you want to send me the FQDN via PM I'll run it through my DNS Stuff account and see if it points out any warnings or errors.

#4 1dmf

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Posted 30 March 2009 - 09:49 AM

The FQDN is an internal server name (netbois), not available externally, which is why I had to add a HOST(a) record. I've also created a PTR reverse DNS record in the AD. the IP is also internal 172.x.x.x

I think it's likely to be an MS server issue for local domain as the missus is having the same problem.

all this should be resolving internaly with the AD (Active Directory), but I am using the word 'Should' and 'MS' in the same sentence lol.gif



#5 Jill

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Posted 30 March 2009 - 11:31 AM

Offtopic
QUOTE(1dmf @ Mar 30 2009, 08:10 AM) View Post
really, what I do wrong dntknw.gif


Sorry, there were inadvertent empty links in the post that I edited out, that's all!


#6 1dmf

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Posted 30 March 2009 - 12:38 PM

phew.gif, I was scratching my head wondering what forum rule i'd inadvertantly broken!

QUOTE
all this should be resolving internaly with the AD (Active Directory)
And as I said if I do an NSLOOKUP via dos prompt it is resolving correctly FQDN -> IP , it's PING that's having the problem, and our systems when trying to access the Webserver SQL DB the other end of the VPN Tunnel.

Yet if I ping the IP it replies... very odd indeed.

#7 Randy

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Posted 30 March 2009 - 02:06 PM

QUOTE
but I am using the word 'Should' and 'MS' in the same sentence


Sorry, I can't help ya with that one. giggle.gif

On a more serious note, you don't have some firewall rules set up somewhere on your internal network that blocks off the ports SQL queries is trying to use or Ping do you? I know it sounds obvious, but many firewall packages --both software and hardware based-- will block off some of those more sensitive ports that tend to get hammered by the hacker wannabe's. As well as Ping. All of my production and backup servers block ping requests at the firewall and block connections to the standard 3306 MySQL port from anything outside the network, cept for the few exceptions I make in the firewall rules so my backup servers can grab backups.

You can't ping to a specific port number if memory serves. You can use ping with the -a flag to have it resolve ip addresses to hostnames. That said, have you tried doing another type of query to the IP number, but including the normal SQL port to see if that goes through? It might tell you if there's an issue in the hostname resolving or potentially a firewall blocking the port.

#8 1dmf

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Posted 31 March 2009 - 03:49 AM

Well I have to assume it's not the firewall as that would stop all traffic all the time woudn't it? if it is a specific port closed, but i have those SQL ports open anyway with forwarding rules so the webserver can talk to our inhouse membership SQL DB on our inhouse SBS 2003 server.

Plus it works fine 99.9% of the time, just on the odd day at some random point, it freezes for @ 15 mins, and is then OK.

I was talking with the missus last night and I did realise the faux pas I made claiming it was a FQDN, when technically it's not, in terms of DNS it's a subdomain i'm pinging.

The FQDN is ComputerName.InternalDomain.local , which I haven't tried I've just pinged ComputerName (subdomain), but that resolves with nslookup anyhow , so again I can't see that being the problem, but next time it happens I will try the FQDN and see if it makes any difference.

Though I'm not ruling out a problem with the firewall as we are talking the firewall->firewall DES encrtyped VPN tunnel between us and the webserver location.

Also the missus is the same as it's the connection between the two office locations and their respective exchange servers, though they have a dedicated lease line connection not VPN over standard internet. But again we use the same ISP so it could be that.

Hmm.... i'm well and truely confused dot com!

#9 1dmf

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Posted 02 April 2009 - 04:04 AM

Happened again today, and the FQDN didn't work.

I've got our server support company involved now, but they are just as puzzled, oh well, guess we'll just have to keep at it till we find the cause!




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