DNS Subnet Prioritization

Question

_{Wednesday, February 1, 2012 3:06 PM}

Hey,

I have a very specific scenario here and I was wondering if anyone could shed some light on how DNS will handle it.

Basically, on our internal network I want to deploy multi web servers. These are split across multiple subnets.

So for example, I have

WebServerA on 10.3.101.167

WebServerB on 10.36.6.20

WebServerC on 10.12.1.100

WebServerD on 10.3.230.141

I have multiple A records of myWebService.net pointing to these four IP addresses.

The interesting part is, I have clients on the following IP addresses

ClientA 10.3.200.57

ClientB 10.33.8.13

ClentC 10.160.7.24

ClientD 10.49.4.201

What would be the order returned for each of these clients?

Will this use Subnet Priority or Round Robin?

All replies (13)

_{Wednesday, February 1, 2012 3:06 PM ✅Answered | 1 vote}

Hello,

Please read this links:

Configuring Subnet Prioritization

Prioritizing local subnets

Other great articles:

DNS and Subnet Priortization & DNS Round Robin (Ace Fekay - MVP)

What is DNS round robin and subnet prioritization?

How can I enable or disable subnet prioritization on the DNS server?

Regards

_{Thursday, February 2, 2012 10:59 AM ✅Answered}

Hi ZeniTimes,

Thanks for update.

If we have set dedicate subnet and IP segment for each site then client will pick up the “closest” address (same IP segment) form the queried address list where get form DNS server .

We can first have a test in lab and see how is going.

Regards,

Tiger Li

TechNet Subscriber Support in forum

If you have any feedback on our support, please contact  [email protected].

Tiger Li

TechNet Community Support

_{Thursday, February 2, 2012 3:54 PM ✅Answered}

 

If we have set dedicate subnet and IP segment for each site then client will pick up the “closest” address (same IP segment) form the queried address list where get form DNS server .

Or, if you prefer, the nearest "mask"; the DNS server will try finding out if which IP best matches the client subnet and prioritize that one; the operation is carried on by checking the client IP and then reordering the RRs (response records) so that the first one returned will be the one closest to the client IP (subnet); the whole mechanism is explained quite clearly here and here 

_{Wednesday, February 1, 2012 2:54 PM}

Hey,

I have a very specific scenario here and I was wondering if anyone could shed some light on how DNS will handle it.

Basically, on our internal network I want to deploy multi web servers. These are split across multiple subnets.

So for example, I have

WebServerA on 10.3.101.167

WebServerB on 10.36.6.20

WebServerC on 10.12.1.100

WebServerD on 10.3.230.141

I have multiple A records of myWebService.net pointing to these four IP addresses.

The interesting part is, I have clients on the following IP addresses

ClientA 10.3.200.57

ClientB 10.33.8.13

ClentC 10.160.7.24

ClientD 10.49.4.201

What would be the order returned for each of these clients?

Will this use Subnet Priority or Round Robin?

_{Wednesday, February 1, 2012 3:04 PM}

Hello,

networking questions are better located in: http://social.technet.microsoft.com/Forums/en/winserverNIS/threads

Best regards Meinolf Weber Disclaimer: This posting is provided "AS IS" with no warranties or guarantees , and confers no rights.

_{Wednesday, February 1, 2012 3:07 PM}

thanks, I'll move the thread across

_{Wednesday, February 1, 2012 4:56 PM}

The ip address is not much help unless you also provide the subnet mask.If you have corectly configured routing between subnets and if you have enabled Round Robin then I think that is what it will use.MCTS - Please remember to click “Mark as Answer” on the post that helps you, and to click “Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread. http://mariusene.wordpress.com/

_{Wednesday, February 1, 2012 5:46 PM}

You can implement what we called a DirectAccess servers, which can be installed in multiple sites of an organization to increase capacity and provide more efficient routing when accessing site-specific intranet resources.

A DirectAccess client can connect to the DirectAccess server of any site and can access the intranet resources in that site.

A DirectAccess client can be managed by a management server of any site.

A DirectAccess client can travel to any site and determine that it is connected to the intranet.

Use the diagram:

_{Thursday, February 2, 2012 2:48 AM | 1 vote}

Hi ZeniTimes,

Thanks for posting here.

>I have multiple A records of myWebService.net pointing to these four IP addresses.

So are these A records have same host name with different IP addresses or different host names (WebServerA, WebServerB..etc) with pointing to its corresponding IP address ?

DNS server will return the address that it has base on the FQDN that client queries. For example when we want to query a FQDN “WebServerA.myWebService.net” then DNS server will return the address 10.3.101.167 that we assigned for A record “WebServerA” under zone “myWebService.net” on DNS server.

Round Robin is another mechanism about has multi records with same hostname and different IP addresses , we can get the detail explanation form the links in Patris_70’s reply and the blog post below is also helpful.

DNS Round Robin and Destination IP address selection

http://blogs.technet.com/b/networking/archive/2009/04/17/dns-round-robin-and-destination-ip-address-selection.aspx

And it’s appreciated that if can discuss your goal more clearly .

Regards,

Tiger Li

TechNet Subscriber Support in forum

If you have any feedback on our support, please contact  [email protected].

Tiger Li

TechNet Community Support

_{Thursday, February 2, 2012 6:51 AM | 1 vote}

Hello George,

Yes direct access would be great but it only works if you have IPv6. You could make it work for IPv4 if you deploy Forefront UAG. In both cases the complexity increases substantially. In order to deploy IPv6 you have to do an audit on your infrastructure for ex. if your routers, L3 switches, printers, applications support IPv6... so the challenge would be great.

MCTS - Please remember to click “Mark as Answer” on the post that helps you, and to click “Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread. http://mariusene.wordpress.com/

_{Thursday, February 2, 2012 10:41 AM}

Hey Tiger,

Thanks for this

I have multiple A records with the same host name pointing to different IP addresses.

Essentially what I have is a highly distributed environment spanning the globe. Rather then having everyone come back to the central data centre, I was think to distribute this to local web servers.

I've had a look at how DNS is setup, both subnet priority and round robin are enable on the DNS server. Is there any way I can enable/ disable this at the Zone level?

_{Thursday, February 2, 2012 10:42 AM}

We don't use IPv6 internally

_{Friday, February 3, 2012 1:56 AM}

Hi ZeniTimes,

Please feel free to let us know if the information was helpful to you.

Regards,

Tiger Li

TechNet Subscriber Support in forum
If you have any feedback on our support, please contact  [email protected].

Tiger Li

TechNet Community Support