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Subnet prioritizing, Round Robin and TTL question RRS feed

  • Question

  • Hi,

    I'm having some doubts about something that my boss came up right now.

    Here in our organization we use the subnet prioritizing and the Round Robin enabled.

    We opted to do it reading this post: http://blogs.msmvps.com/acefekay/2010/05/29/dns-and-subnet-priortization-amp-dns-round-robin/

    Since our EPM server has three A records with different IP addresses, and when I tried to ping it inside my network it kept me returning a different IP address. Enabling subnet prioritizing and configuring it for our network mask (/21) resolved the problem.

    Now my boss wants to make this scenario possible:

    Server name: webtest

    A record1: 192.168.46.193

    A record2: 172.16.46.2

    Pinging the webtest server inside a 192.168.46.0/21 PC, it returns the A record1.

    When it is off-line, the ping returns the A record2.

    Using the subnet prioritizing it is impossible, since the priority is this:

    First - Subnet priority

    Second - Round Robin

    Disabling subnet prioritizing and changing TTL of the RR for the server should resolve it?

    PS: In time, the network 172.16.46.0 is reached from our network

    Update! Tried this now:

    Added a second IP address to my network card. So I have: 192.168.46.184 and 192.168.46.187 IP addresses. When I try to ping it always returns the 187 record... it isn't supposed to rotate the results between 184 and 187?

    We are using two Windows Server 2008 R2 and one Windows Server 2008 servers. The forest and domain functional levels are Windows Server 2003


    Friday, January 29, 2016 4:08 PM

Answers

  • Cartman,

    Hi again.

    The problem is that it was the first thing she tried to do in Windows Server 2008 R2 and didn't worked. That's why I asked about Windows Server 2012.

    But thinking about it... whe have 3 DNS servers in our environment. Maybe it was a problem of waiting for replicating the configuration...

    Even so, I told her that this is not a good practice to use DNS to do this kind of solution. I think that the best solution is something on the server-side, like you told me before.

    Thanks once again!

    Tuesday, February 2, 2016 10:52 AM

All replies

  • >> Disabling subnet prioritizing and changing TTL of the RR for the server should resolve it?

       According your description, I think you want to do a Hot Standby for a server with two IP address in the different subnet, I am afraid there is no such function in Win DNS server, You should do it in server-side, not in the DNS.

    >>When I try to ping it always returns the 187 record...

    When you lookup a DNS RR, do not use PING,PING may not use DNS to resolve, it could use cache .  Clear the cache(both client and server) ,and use NSLOOKUP try again.

     

    Best Regards,Cartman

    ---------------------------------------------------------------------------------------------------------------------------

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    Monday, February 1, 2016 6:53 AM
  • Cartman,

    I was thinking about that on the same day...

    Thanks a lot for your time and attention!

    Monday, February 1, 2016 3:44 PM
  • Cartman,

    New information about this: My boss tried the same scenario on a Windows Server 2012, and... it worked the way she wanted to...

    She created the two DNS records with different IP addresses and configured the TTL to 1 second.

    When she pings the server name with both servers online, it returns the firts IP address, when she turns off the first server it takes almost 30 seconds and starts pinging the second IP address. If she turns the first server on, it takes no longer than the time of the server to initialize again and returns to ping the first server...

    Is it something that only Windows Server 2012 have? Anyone?


    Monday, February 1, 2016 4:52 PM
  • >> Is it something that only Windows Server 2012 have?

              

               It seems your boss modified the TTL to work around this scenario.

               The TTL value determines how long the data is cached on client.

               Thank you for sharing this to us, if you have other questions, feel free to here.

    Best Regards,

    Cartman


    Please remember to mark the replies as answers if they help and unmark them if they provide no help. If you have feedback for TechNet Support, contact tnmff@microsoft.com.


    Tuesday, February 2, 2016 2:52 AM
  • Cartman,

    Hi again.

    The problem is that it was the first thing she tried to do in Windows Server 2008 R2 and didn't worked. That's why I asked about Windows Server 2012.

    But thinking about it... whe have 3 DNS servers in our environment. Maybe it was a problem of waiting for replicating the configuration...

    Even so, I told her that this is not a good practice to use DNS to do this kind of solution. I think that the best solution is something on the server-side, like you told me before.

    Thanks once again!

    Tuesday, February 2, 2016 10:52 AM