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srivatsavat92's avatar
srivatsavat92
Icon for Nimbostratus rankNimbostratus
Oct 04, 2022

CNAME Monitoring

Hello All,

We have a requirement where we are creating a setup on GTM. 2 pools and each pool have 1 Member which is a CNAME entry and not an A - Record. But we are facing challenge on how to do health check Monitor to that C-NAME.

Here we have 2 pools and if one pool goes down traffic should go to another pool. We can do it for A-Record becuase we can setup a monitor for it. But i dont see an option for Setting up a monitor for C-NAME.

Please help.

application delivery
  • rob_carr's avatar
    rob_carr
    Icon for Cirrocumulus rankCirrocumulus
    Oct 05, 2022

    Hi srivatsavat92,
    We do this to provide access to cloud-specific workloads that need access to a service. We use both GTM and LTM for this solution.

    Wide IPs-
    cloudagnosticname.example.com, type CNAME
    cspAname.example.com, type A
    cspBname.example.com, type A

    Pools -
    cnpool_cloudagnosticname { type CNAME, members are Wide IPs cloudproviderAname.example.com & cloudproviderBname.example.com }
    vspool_cspAname { type A, member is VS for service in cloudproviderA }
    vspool_cspBname { type A, member is VS for service in cloudproviderB }

    Wide IP cloudagnosticname.example.com --> CNAME pool cnpool_cloudagnosticname

    CNAME pool cnpool_cloudagnosticname --> Wide IP cspAname.example.com & Wide IP cspBname.example.com

    Health of the two members of cnpool_cloudagnisticname is determined by the health of the two Wide IPs.

    Wide IP cspAname.example.com --> A pool vspool_cspAname
    Wide IP cspBname.example.com --> A pool vspool_cspBname

    Federated LTMs provide health information on the VSs back to the BIG-IP DNS cluster. As long as the VS is up, the cloud specific Wide IP is up and the member of the CNAME pool is up as well. If a VS goes down, the cloud specific Wide IP goes down, as does the member of the CNAME pool. The cloudagnosticname.example.com Wide IP only ever hands out 'healthy' CNAMEs.

    You could do this without using LTMs to provide the health information, you would just need to configure server and virtual server objects that correspond to the hosts that the cloud specific Wide IPs represent and monitor them from your BIG-IP DNS cluster directly.