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DNS access issue over a corporate LAN

We have two networks, two separate domains connected via an MPLS connection.  On either side of the network is an ASA firewall and on my side of the network this simply acts as a router sending all internal Internet traffic out to our ISP and all other traffic to the other network.  Both networks carry the other sides DNS added locally as a secondary zone.  On my side we push out a domain suffix list via group policy including both domains.  Based on this we access a JDE ERP system in the second network and connect via IE over the MPLS to the servers in the second network.  

The problem arrives with users on our network that has fixed IP addresses.  At seemingly random intervals they lose connection to the ERP servers in the other network.  This issue always resolves itself after a brief loss of connection but can happen several times a day or hour.  When I look at these stations IP and DNS seem fine and I can resolve pings to the other network but cannot access the JDE servers.  Users on DHCP are not affected.

This seems like a DNS issue but I am struggling to resolve it.  

Any thoughts or ideas are welcome.      
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DHPBilcare
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DHPBilcare
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2 Solutions
 
Hypercat (Deb)Commented:
I suspect it is not DNS-related since presumably the DHCP and non-DHCP clients are using the same DNS servers. Check the NIC properties on the problem clients to be sure that "Enable NetBIOS over TCP/IP" is checked.  
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Jeremy WeisingerSenior Network Consultant / EngineerCommented:
It doesn't really sound like DNS to me. I would check the TCP/IP settings on all your statically configured computers to make sure they have the proper IP addresses and subnets. Also check for IP conflicts and make sure there are exclusions in DHCP for any statically configured nodes. The intermittent problems with the static computers make me think this might be the issue.
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OriNetworksCommented:
By any chance is the network bandwidth maxing out? This would explain the random and short loss of connectivity. Is it only one site experiencing this issue, if not, maybe its the link where the JDE servers are.
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OriNetworksCommented:
Also agree with above. Make sure there are no IP conflicts and that DHCP has exclusions for the ranges that you have static IP assigned.
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DHPBilcareAuthor Commented:
Thanks for the quick responses,

I will check the NetBios settings and potential conflicts tomorrow.  

There is only one remote site to the JDE servers and that's us.  If it were a timeout issue with the link presumably this would affect all clients and not just the ones on fixed IP?    
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DHPBilcareAuthor Commented:
We dont currently have exclusions for the IP's in question but they are out of range of the pool of available IP's for DHCP.
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Jeremy WeisingerSenior Network Consultant / EngineerCommented:
As long as they're out of the range then you should be fine. Can you shutdown one of the computers that is having issues and then ping it's IP address and see if anything responds? (Ideally you would do this for all the computers having issues)
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DHPBilcareAuthor Commented:
Definetly not an IP conflict.

Not sure what else I can test.
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Hypercat (Deb)Commented:
What you need to do first is to be sure that all workstations are using the same TCP/IP settings (DNS, NetBios, domain suffixes, etc.). What I would recommend if possible  is to use DHCP reservations for the workstations that need static IPs, instead of using manually assigned static IPs. That way, those workstations would still get the benefit of the DHCP scope options, and you would be assured that TCP/IP settings are consistent across all workstations. Once you've done that, if those workstations are still having problems, then we need to look elsewhere to figure out what's happening.
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DHPBilcareAuthor Commented:
Interesting...

I push out a DNS suffix list to all clients which includes the two domains.  

One one of the affected coputers I added the suffix list locally and for a week know it has not had any issues.  However the other affected clients are all on Windows 7 and the options to amend the local suffix is greyed out...  
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Hypercat (Deb)Commented:
You'd definitely have to have administrator rights to change these settings, but I assume you are logged on with local admin rights and it's still greyed out?
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Hypercat (Deb)Commented:
See if this thread is helpful - it seems to have some suggestions on how to enable this:

http://social.technet.microsoft.com/Forums/en/w7itpronetworking/thread/76d07f31-62d6-4648-a3e2-7e6e16791363
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DHPBilcareAuthor Commented:
Thanks for that.  The options are still greyed out on the MS7 client.  
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DHPBilcareAuthor Commented:
Can't explain why but the user reports that the problem has seemingly resolved itself with no explanation as to why??  

The only thing that has changed is that he has installed SP1??  

I will watch how this goes for a few more days and then close the question.  
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Hypercat (Deb)Commented:
Weird. I wonder if SP1 has some sort of update to the NLA function or something like that.  I have experienced some strange problems with NLA on Vista machines but haven't ever had an issue with a Windows 7 workstation.
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DHPBilcareAuthor Commented:
The problem has resurfaced after two days.

I've added the affected user onto a DHCP reservation and see if this works.
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