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DNS-Multiple value priority

Posted on 2006-11-19
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Last Modified: 2010-03-18
I have 2 windows 2003 servers, one of which is a DC, GC etc and a DNS for the internal network. The other server is also a DNS, configured to synchronise with the first.

Server1 has 3 network adaptors. Server 2 has 2 network adaptors. One adaptor in each is connected to a Gigabit ethernet adaptor and is used for the backup (backup runs from server 2 and backs up data from server1 amongst other things)

until recently, this was working fine - veritas was set to use the gigabit ethernet adapter by default and it was doing so. However, recently it has used the 100MBPS adaptor, causing a massive increase in backup time!!! I notice if I perform a nslookup, it returns the address of the 100MBPS adapter in server1.

How can I change the order in which addresses are given out from the DNS?

It's the standard DNS built into windows 2003.

thanks in advance.
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Question by:Ice123
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by:Steve Knight
ID: 17975851
Well assuming this is only used for gigabit the obvious thing to do here is to de-register the gigabit adaptor from being added to DNS and configure the backup program to use the IP address on that segment or add another hostname, e.g. server1-backup to DNS with the IP of the gigabit card and configure Veritas to use that IP / name.   I presume you are using a different address range for this and either a small gigabit switch or a crossover cable between them for the backup connection?  Otherwise you could look into adding both connections onto the main LAN and using load balancing for fault-tolerance and therefore use both cards for normal and backups?

By default Windows 200x DNS will give out the closest IP address, i.e. if you are on subnet 192.168.0.1 and one of the addresses is on the 192.168.0.x subnet it will always get that one.

What is the third NIC in server2 for BTW -- internet access?

Steve
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by:data_grrr
ID: 17980210
when a dns A record has two ip addresses, windows determines the priority by looking the LocalNetPriority registry parameter.

it's in HKLM\SYSTEM\CurrentControlSet\Services\DNS\Parameters

the default is "1". it means dns will give the most similar address.

but if you make it "0" it will give the address in the order they were added to the dns by you.

you can do this, by using regedit and then restart the dns service.

but without restarting you may use DNS console. Right-click the server name, click Properties,  and then click the Advanced  tab. then uncheck enable netmask ordering.

if it doesn't work re-add the dns records in the order you prefer.

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by:Steve Knight
ID: 17980242
I imagine in this case though normal clients probably want to get IP address "a" on the users' card and backup server IP address "b" ... Ice123, any feedback please/
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Author Comment

by:Ice123
ID: 17981752
Hi Guys,

thanks for the feedback. I will give those suggestions a shot.

Just to clarify, one network (main access which clients all connect through) on 192.168.1.x
second network is just for communication between a total of three servers on 192.168.2.x
third card is connected to another network that leads to the internet. None of these networks are physically connected together.

Yes, I want servers to use network 2 as default inter-communication, but obviously the clients can only access through network 1.

thanks
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by:Steve Knight
ID: 17982509
You might also find that binding order comes into it --> If you want the servers to talk to each other over card2 then put card2 at the top of the binding order -- You find this in Network control panel, then Advanced | Advanced Options  (or thereabouts).  Push the card for the servers to use to the top on each then the user's ones next and the internet one last.

The users will come in on the second card down and traffic will go back out the same way.

Steve
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Author Comment

by:Ice123
ID: 17986673
I tried both of the suggestions above - changing the DNS order, and changing the network order. Neither of these actually solved the problem. When I ping, I am still getting the same order of results - i.e. the public ip address first, therefore it uses this address to communicate. Also copying files it is still using the public interfact (as opposed to the Gigabit server connections!)

any further suggestions would be greatly appreciated.
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by:Steve Knight
ID: 17987013
You could just to use the IP address or another alias as suggested then I guess.  I'm surprised the binding order did not make a difference.  Have you done a

ipconfig /flushdns

after making any of the changes?

Any particular reason why you have gigabit for the servers to talk to each other and only 100 meg to your users...  I can see a logical one, i.e. there are no gigabit switches connecting to the users I suppose.

Steve
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Author Comment

by:Ice123
ID: 17989958
no - hadnt tried that dnsflush! thanks!
Just having a play to see what happens. when you perform an nslookup, does it matter what order the addresses are listed in?

Reason for 100Mbit to clients is simply that the cost of gigabit switches upon installation was not justifyable. The connection does not need to be that fast. However, there is a lot of data replicated between servers, so a small switch was purchased for just that reason.

will post back later with results.
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Author Comment

by:Ice123
ID: 18059896
I have tried all of the above now with the exception of a second alias.

If I want to create a second alias, how do I do that? Veritas will not accept manually inputed names such as \\newalias. Therefore how can i create a new alias that can be picked up as if it was a different computer by veritas.

cheers,
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Author Comment

by:Ice123
ID: 18540941
Have given up in the end and simply purchased Gigabit switches for entire network! Works much better now.
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by:Steve Knight
ID: 18540998
It is sometimes the easier option....
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