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iSCSI NIC registerning in DNS

Posted on 2010-11-28
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I have a iSCSI SAN.
I have installed a iSCSI NIC in my DC/DNS server and advertised storage fine.
Problem is that the NIC is registering itself in DNS and PCs are resolving the host to the iSCSI IP address.
I have unticked the checkbox to register in DNS, changed the order of the NIC in advanced options to the bottom
but it makes no difference. Any ideas?
It is Windows Server 2008.
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Question by:SteveSext
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12 Comments
 
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by:
tstritof earned 1000 total points
ID: 34227123
Hi,

have you tried to manually remove the A record in Forward Lookup Zone and PTR record in Reverse Lookup Zone of your iSCSI NIC from DNS after unticking it in NIC properties? These records won't get deleted immediately after you change the NIC settings.

You should also clear the DNS cache on server and clients after that.

Regards,
Tomislav

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by:kevinhsieh
ID: 34227270
Having multiple NICs on a domain controller is a bad idea, and this is one of the reasons why. You can try to make a static entry for the DC in DNS. That prevents normal machines from making dynamic updates to DNS, but I don't know if that works for DCs. If it doesn't, you should disable the NIC being used for iSCSI and just use your main NIC to talk to your SAN. That's not "best practice", but unless your SAN is completely isolated from the rest of your network such that it won't work, I can't make a convincing arguement as to why it won't work or why it really, really shouldn't be done. Performance will be fine, and security probably won't change either.
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by:tstritof
ID: 34227317
I think the configuration with multiple NICs on DC gets blamed too often. I have W2K8 DCs configured with multiple NICs (even SBS), some running as routers, some running virtual machines in Hyper-V all with no issues. The only thing I always do to keep out of problems is disable the IPv6 protocol on all NICs, if necessary disable registration of certain NICs in DNS and make sure my DNS listens only on a single chosen IP address.

Also since I believe iSCSI NICs usually use offloading quite heavily to keep the CPU from melting and I've seen that same offloading cause grief with normal network traffic (especially with some Broadcom models) I'm somewhat worried about the outcome of single NIC scenario.
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by:kevinhsieh
ID: 34227334
My thinking is that if there is so much iSCSI traffic such to the point where a single NIC really would be a problem, the author wouldn't be trying to run the file server/SQL server/Exchange server/whatever on a domain controller in the first place.
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by:tstritof
ID: 34227366
I don't know what will else might or might not be running on Steve's machine. What I meant was that having multiple NICs on a DC is more of a controllable configuration issue compared to unknown potential issues in one NIC scenario with iSCSI. Sorry if that came ot wrong.
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by:tstritof
ID: 34227368
:) out...
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Assisted Solution

by:msmamji
msmamji earned 1000 total points
ID: 34229183
If your iSCSI is getting address from the DHCP then there is a possibility that the DHCP might be registering the IP to the DNS on your (machine's) behalf. If that is the case try assiging a static IP to the iSCSI NIC.
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Author Comment

by:SteveSext
ID: 34229238
The iscsi nics have assigned static addresses fom my storage subnet.
I've disabled al checkboxes in nic properties, disabed lmhosts, made no difference.
Any other ideas??
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by:msmamji
ID: 34229378
did you remove the DNS records from the DNS server after that
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by:tstritof
ID: 34229577
Have you disabled NetBIOS? If primary domain suffix gets applied there the fqdn will be popping around again with NetBIOS enabled.

If you want to be sure no other interference comes from that NIC disable all protocols you don't need for your iSCSI and go rechek the Tcpip settings for that NIC directly in registry to make sur they got applied (I haven't seen that problem on W2K8 machine yet, but...)

When cleaning DNS make sure you clean out ALL A records pointing to the wrong IP address and that you disable all but 1 desired address as DNS listener in DNS server (or your nameserver will be registering under multiple addresses again).

Clear the DNS cache. Do a restart after the cleanup process. Clear DNS cache on your clients and retest.

Regards,
Tomislav
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by:kevinhsieh
ID: 34233155
Did you try my idea of deleting all DNS entries and putting in a static entry? Otherwise, I suggest going to 1 NIC, or enable everything on the iSCSI NICs so that if clients use that IP that it will work (as long as they can route to it).
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by:andyalder
ID: 34237704
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