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JohnRhonda_2200's avatar
JohnRhonda_2200
Icon for Nimbostratus rankNimbostratus
Sep 01, 2015

GTM Topology - LDNS Request

Hello!

I have some doubts how the GTM works in its Topology LB records.

If I have the following:

WIP             Pool
www.mydomain.com        Pool A <- Prefered: Topology, Alternate: Round Robin, Fallback:Return to DNS
www.otherdomain.com     Pool B <- Prefered: Topology, Alternate: Round Robin, Fallback:Return to DNS
www.onedomain.com       Pool C <- Prefered: Topology, Alternate: Round Robin, Fallback:Return to DNS
www.lastdomain.com      Pool D <- Prefered: Topology, Alternate: Round Robin, Fallback:Return to DNS



Order   LDNS Request Source Destination     Weight
  1     10.20.0.0/16        Pool A      1
  2     10.30.0.0/16        Pool B      1
  3     10.40.0.0/16        Pool A      1
  4     10.0.0.0/16     Pool D      1

My Scenario Question are:

1- If a query is made for "www.mydomain.com" from source IP 10.20.0.1, Is Pool A served?

2- If a query is made for "www.mydomain.com" from source IP 192.168.10.1, Will Round Robin be served?

3- If a query is made for "www.lastdomain.com" from source IP 10.20.0.1, Is Pool D served? Will Topology logic not catch the first line 10.20.0.0/16 > Pool A?

Thank you

JohnR

BIG-IP DNS
ldns
topology

7 Replies

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  • Brad_Parker_139's avatar
    Brad_Parker_139
    Icon for Nacreous rankNacreous
    Sep 01, 2015

    Your setup here isn't quite complete to make valid assumptions because you have load balancing methods between pools configured for the wideIP as well as load balancing methods within the pools.

     

    How are you load balancing at the wideIP pool level? I assume the above "Prefered: Topology, Alternate: Round Robin, Fallback:Return to DNS" is the load balancing config within the pool?

     

    • Brad_Parker_139's avatar
      Brad_Parker_139
      Icon for Nacreous rankNacreous
      Sep 01, 2015
      So each Wide IP has pools A, B, C, and D? and the wide IP is setup for Topology? or each wide IP has one pool with the above methods within the pool?
  • Brad_Parker's avatar
    Brad_Parker
    Icon for Cirrus rankCirrus
    Sep 01, 2015

    Your setup here isn't quite complete to make valid assumptions because you have load balancing methods between pools configured for the wideIP as well as load balancing methods within the pools.

     

    How are you load balancing at the wideIP pool level? I assume the above "Prefered: Topology, Alternate: Round Robin, Fallback:Return to DNS" is the load balancing config within the pool?

     

    • Brad_Parker's avatar
      Brad_Parker
      Icon for Cirrus rankCirrus
      Sep 01, 2015
      So each Wide IP has pools A, B, C, and D? and the wide IP is setup for Topology? or each wide IP has one pool with the above methods within the pool?
  • nathe's avatar
    nathe
    Icon for Cirrocumulus rankCirrocumulus
    Sep 02, 2015

    Hi John,

     

    I agree with Brad on this, your load balancing looks a bit confused on this, perhaps we're not seeing the whole story.

     

    If the WIP only has one Pool i.e. www.mydomain.com has just Pool A, then no load balancing occurs. Once Pool A is chosen then the LB algorithm is Topology, however, none of your topology records will match. This is because topology records are associated to Wide IPs or Pools for which they are appropriate. For instance, ones that choose a pool are only associated with WIPS that use that pool and ones that choose a virtual server are only associated with pools which have those virtual servers as members. Hope that makes sense. In example 1, www.mydomain.com will chose a pool member in Pool A using Round Robin. In example 2, again Pool A and in example 3 Pool D. That's my guess anyway on the info above.

     

    Best practice seen is get the Wide IP to choose from a number of Pools using Topology and Pools to choose from a number of virtual servers on a Data Centre basis using Topology.

     

    Hope this helps, be great if you could come back to DC with your setup confirmed.

     

    N