AD and DNS Subnet Ordering

[gingerdazza]

Hi.

We have a Win2k AD, and all our DNS servers have "subnet ordering"
enabled. It's causing an issue with a DNS RR record we have as I want
users to ALWAYS get alternated between the two A records of a
particular host called "server1". DNS seems to be running some sort of
algorithm and some hosts always get the the two server1 A records in
the same order

i.e.

1.1.1.1
1.1.1.2

.....even after flushing the local client DNS cache. Round Robin is also
enabled on DNS servers.

I want it to ALWAYS be the case that, no matter what subnet a DNS query
comes from, the DNS servers always alternate server1

i.e. gives the above order to query1, and then swaps the order for
query2, then back again for query3 etc etc.

To do this, do I need to turn off "subnet ordering"? And if so, does
this affect AD at all (i.e. perhaps affect clients' DC logon servers
etc)?

Thanks

 

[Ace Fekay [MVP]]

In

Hi.

We have a Win2k AD, and all our DNS servers have "subnet ordering"
enabled. It's causing an issue with a DNS RR record we have as I want
users to ALWAYS get alternated between the two A records of a
particular host called "server1". DNS seems to be running some sort of
algorithm and some hosts always get the the two server1 A records in
the same order

i.e.

1.1.1.1
1.1.1.2

....even after flushing the local client DNS cache. Round Robin is
also enabled on DNS servers.

I want it to ALWAYS be the case that, no matter what subnet a DNS
query comes from, the DNS servers always alternate server1

i.e. gives the above order to query1, and then swaps the order for
query2, then back again for query3 etc etc.

To do this, do I need to turn off "subnet ordering"? And if so, does
this affect AD at all (i.e. perhaps affect clients' DC logon servers
etc)?

Thanks

The example you show above shows two IPs in the same subnet. Therefore,
Subnetmask Ordering wouldn't be the problem. If they are different IPs, and
the client is from the same subnet that matches one of the records, but not
the other record, then it will always get the IP on the subnet that closely
matches it's own IP.

If you test this with nslookup, it will show the two results. If you hit
arrow up and run it again and again, it should rotate.

I hope these aren't DCs. What type of servers and functions do they offer?

--
Ace

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Ace Fekay, MCSE 2003 & 2000, MCSA 2003 & 2000, MCSE+I, MCT, MVP
Microsoft MVP - Windows Server Directory Services
Microsoft Certified Trainer
Infinite Diversities in Infinite Combinations.
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