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How to create dns entry for 1 host two ip addresses RRS feed

  • Question

  • I have a scenario where I have to add a proxy setting into dns. I have two nodes with obviosly two seperate ip addresses and i want to create one record that help if one node goes down the other one would still be on line so we have no loss of service so redundancy is there

    we currently run windows 2008 DNS

    Many Thanks

    Friday, May 28, 2010 9:42 AM

Answers

  • I have a scenario where I have to add a proxy setting into dns. I have two nodes with obviosly two seperate ip addresses and i want to create one record that help if one node goes down the other one would still be on line so we have no loss of service so redundancy is there

    we currently run windows 2008 DNS

    Many Thanks

    Hello mburguk,

    To create multiple A (Host Records) with the same IP, simply create a new A (Host) record, and give it IP #1. Then create another A (Host) record, giving it the same IP address. You can add as many as you like. DNS Round Robin feature will rotate responses for each query. You can test it with nslookup.

    nslookup
    proxy.domain.com (hit Enter)
    Then do it again by hitting the arrow Up key, hit enter

    You will notice responses toggle back and forth between the two IPs.

    However, the only issue I see is you may need to disable Round Robin. The reason being is that if a client queries for the record and gets say, ISA1, and a site they've visited is cached in ISA1, then after ISA1's A record's TTL expires in the client side cache, it will send another query and may get ISA2's IP. In this case, ISA2 will not have it cached, and will need to load the site from scratch. 

    I actually don't recommend disabling Round Robin because it may effect AD resources, to an extent, such as Round Robin between DCs in a client's AD site with the LdapIpAddress.

    If you have ISA Enterprise, you can create an Array with two ISA severs using the Array's name and its IP address. An Array overcomes this issue because all ISA servers in the array will share their cache with each other. All clients can query the single name for the single IP, and it will be directed to the array. If not using ISA, you would need to check the documentation to see if it offers this feature.

    If interested, please read the following for more info about ISA arrays:

    Configuring ISA Server Arrays
    http://www.isaserver.org/tutorials/Configuring_ISA_Server_Arrays.html

    I hope that helps.

    Ace

     


    Ace Fekay, MVP, MCT, MCITP EA, MCTS Windows 2008 & Exchange 2007, MCSE & MCSA 2003/2000, MCSA Messaging 2003 Microsoft Certified Trainer Microsoft MVP - Directory Services This posting is provided AS-IS with no warranties or guarantees and confers no rights.
    Saturday, May 29, 2010 6:06 AM

All replies

  • I have a scenario where I have to add a proxy setting into dns. I have two nodes with obviosly two seperate ip addresses and i want to create one record that help if one node goes down the other one would still be on line so we have no loss of service so redundancy is there

    we currently run windows 2008 DNS

    Many Thanks

    Hello mburguk,

    To create multiple A (Host Records) with the same IP, simply create a new A (Host) record, and give it IP #1. Then create another A (Host) record, giving it the same IP address. You can add as many as you like. DNS Round Robin feature will rotate responses for each query. You can test it with nslookup.

    nslookup
    proxy.domain.com (hit Enter)
    Then do it again by hitting the arrow Up key, hit enter

    You will notice responses toggle back and forth between the two IPs.

    However, the only issue I see is you may need to disable Round Robin. The reason being is that if a client queries for the record and gets say, ISA1, and a site they've visited is cached in ISA1, then after ISA1's A record's TTL expires in the client side cache, it will send another query and may get ISA2's IP. In this case, ISA2 will not have it cached, and will need to load the site from scratch. 

    I actually don't recommend disabling Round Robin because it may effect AD resources, to an extent, such as Round Robin between DCs in a client's AD site with the LdapIpAddress.

    If you have ISA Enterprise, you can create an Array with two ISA severs using the Array's name and its IP address. An Array overcomes this issue because all ISA servers in the array will share their cache with each other. All clients can query the single name for the single IP, and it will be directed to the array. If not using ISA, you would need to check the documentation to see if it offers this feature.

    If interested, please read the following for more info about ISA arrays:

    Configuring ISA Server Arrays
    http://www.isaserver.org/tutorials/Configuring_ISA_Server_Arrays.html

    I hope that helps.

    Ace

     


    Ace Fekay, MVP, MCT, MCITP EA, MCTS Windows 2008 & Exchange 2007, MCSE & MCSA 2003/2000, MCSA Messaging 2003 Microsoft Certified Trainer Microsoft MVP - Directory Services This posting is provided AS-IS with no warranties or guarantees and confers no rights.
    Saturday, May 29, 2010 6:06 AM
  • Thank you very much for your help on this matter, the proxy we are using is a third party product but the concept will be the same
    Wednesday, June 2, 2010 2:01 PM
  • On Wed, 2 Jun 2010 14:01:32 +0000, mburguk wrote:
     
    >Thank you very much for your help on this matter, the proxy we are using is a third party product but the concept will be the same
     
     
    You are welcome! As for the third party product, what I mentioned
    ealier regarding the cache, will still occur. Round Robin does not
    guarantee which proxy IP it will provide, and a client may connect to
    one of the proxies that does not have the client's previously visited
    web page cached, forcing the proxy to retrieve a fresh copy, unless of
    course the proxy being used supports the array feature.
     
    Curious, does it support creating arrays?
     
    Thank you,
    Ace
     

    Ace Fekay, MVP, MCT, MCITP EA, MCTS Windows 2008 & Exchange 2007, MCSE & MCSA 2003/2000, MCSA Messaging 2003 Microsoft Certified Trainer Microsoft MVP - Directory Services This posting is provided AS-IS with no warranties or guarantees and confers no rights.
    Wednesday, June 2, 2010 3:15 PM