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DNS Round robin Server 2003

Posted on 2008-10-01
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Last Modified: 2008-10-06
I am trying to setup DNS round robin and am getting a little stuck. I'm not an expert on DNS and require some help.

Our company has 3 webservers all setup on different IP ranges. All with different websites hosted on IIS6. I want to setup load balancing on the websites and DNS round robin seemed the easiest and cheapest way. Each websever is its own AD\DNS server in its own forest. All have server 2003 with at leat SP1 (we are also about to deploy Sever 2008 as well so please bear that in mind with your answer.) I've looked at various articles on the web but can't quite get my head around them. As it stands I  have a test website thats setup identically on 2 different websevers and I can hit one on it domain name and the other from its IP. The A record in the domain name settings points to 85.xx.xx.xx and this website is working ok.

From what I can gather DNS round robin is as easy as just adding a new A host record in the domain name settings. I've tried doing this and it never adds a new one. Just updates the old record. Unfortunatly the response from freeparking.com which the domain is with is ..

"Our dns manager does not support this function. You can only have 1 www record."

I'm I trying to do this correctly? And is their another way around this? As the severs stand I have not touched any DNS settings on the servers. They are just set as default.
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Question by:4mmdds
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by:Chris Dent
ID: 22612811

If they only permit one www record you cannot use Round Robin for that. Round Robin needs multiple www records for a single resource (in this case, www).

You will always be constrained by your DNS host, your only way around that is to switch DNS host :-\

Chris
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Author Comment

by:4mmdds
ID: 22612897
OK so I was definalty doing this the correct way yes? And I definalty don't need to chaneg any DNS settings on the servers? I've had a word with my Datacentre provider and asked if they can help with the multiple A host records and this was their response:

"We can do this for you no problem. You would just need to tell us what records you want creating, then we can add them to our nameservers. Once we had the records in place, you would then just need to delegate the nameserver operations at the registrar for the domain to our nameservers."

Does this seem like a valid response?
If its ok I'll award the points to you once I've done this and got my test site working ok as I want to make sure that everything is ok first

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by:Chris Dent
ID: 22612908

Yes, and yes to the first two questions. It's only going to be practical configuring Round Robin on the public DNS service.

Yes, it does indeed. They'll take over hosting of the DNS zone and look to be able to provide you with the functionality you need. Much more promising :)

Bear in mind that when making a change like this you will find it takes a day or so for the changes to fully propagate (after changing the name servers for your domain with your registrar).

Chris
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Author Comment

by:4mmdds
ID: 22612945
Ok brilliant.........I'm going to move one over now. If I move the name server over then would freeparking.com still have any use to me....as the IPS tag stays with them? I'm guessing I would just use my data centre hosts for any DNS changes (A host record e.t.c) and other management changes e.g pop3 email mailbox creation e.t.c stays with freeparking?

Yep I reliase that it may take upto a couple of days. Hopefully this will be quick and painless :o)
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by:Chris Dent
ID: 22612983

If the IPS stays with them they're still your registration agent. That should be fine, but it does mean you can't drop them entirely. It should mean that renewals for the domain name go through them.

> and other management changes e.g pop3 email mailbox creation
> e.t.c stays with freeparking?

If those are under the same domain those will move as well. You can't split the zone if they're all at the same level. e.g.

mail.yourdomain.com
www.yourdomain.com
etc

Chris
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Author Comment

by:4mmdds
ID: 22622237
Chris - I can see from using DNS tools on the websites that Roeville.com points to both IPs as requested by my data hosting company but Ive tried viewing www.roeville.com on 4 different ISPs now and they always hit the http://85.91.239.147 address.
I can access my second site on http://85.91.239.163 ok. I've setup a quick difference on the sites - its the full stop after the Symantec software partner logo (bottom left)The original site on .147 doesnt have this. Im just wondering if youve got any clues. I know IE is supposed to cache  the IP somewhere but I have cleared all cache and also flushed my DNS and it still always shows the .147 site.

Any clues
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by:Chris Dent
ID: 22622275

The record alternates correctly for me here, but...

Bear in mind that one a client has a cached record they will use that cached record exclusively. You can see the contents of a Windows client cache with "ipconfig /displaydns".

That shouldn't be a huge problem, your record is only remembered for a minute. After that minute it will request the record again, however there's no guarantee that it will get a different IP address (although it works pretty well for me here, with only me accessing the site).

Chris
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Author Comment

by:4mmdds
ID: 22622291
I'm sure its all ok but I just need to see it from my side  - I'm fussy like that :o)  I had already tried ipconfig /flushdns to clear my cache out - also ran a repair on my network card which I believe does something similair..........still only seeing .147.
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Author Comment

by:4mmdds
ID: 22622307
forgot to mention...........I did at one point have an entry in my host file that forced roeville.com to .147 (used to have a local domain called roeville down here) but I deleted that out yesterday when I start all of this. Is that cached somewhere too?
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Chris Dent earned 500 total points
ID: 22622344

> Is that cached somewhere too?

Nope, that one is checked on each request.

It could be NetMask Ordering if you happen to be connecting from a very similar IP address?

Anyway, we can test it a bit.

Run:

nslookup www.roeville.com
nslookup www.roeville.com

We expect the list returned to change order with each alternate request. Like this:

Non-authoritative answer:
Name:    www.roeville.com
Addresses:  85.91.239.147, 85.91.239.163
...
Non-authoritative answer:
Name:    www.roeville.com
Addresses:  85.91.239.163, 85.91.239.147

See what I mean? That's round robin in operation.

You should see the same behaviour if you do:

ping www.roeville.com
ipconfig /flushdns
ping www.roeville.com
ipconfig /flushdns
etc

If that isn't happening, is the list being returned in the same order each time?

Chris
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Author Comment

by:4mmdds
ID: 22622356
ok my results are:

Non-authoritative answer:
Name:    www.roeville.com
Address:  85.91.239.147

does this just mean that changes haven't propergated yet?

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Expert Comment

by:Chris Dent
ID: 22622368

Potentially, lets see the TTL on that record. Run:

nslookup
set type=debug
www.roeville.com

In the final "Got Answer" section you should see the remaining TTL for the record (that's on the local DNS server). Looks like this:

    ANSWERS:
    ->  www.roeville.com
        internet address = 85.91.239.163
        ttl = 53 (53 secs)
    ->  www.roeville.com
        internet address = 85.91.239.147
        ttl = 53 (53 secs)

As you can see, I have 53 seconds left on the cached record here (that's on my DNS server, not the client). However, that's based on the live TTL of 1 minute. If you changed that yesterday and it was previously much higher then you may still have the old version cached.

Chris
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Author Comment

by:4mmdds
ID: 22647917
All working - sorry I was slow in getting back to you - points are yours.
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Expert Comment

by:Chris Dent
ID: 22647927

No problem at all, glad I could help out.

Chris
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