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2funky_105078's avatar
2funky_105078
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Apr 22, 2014

GTM: avoiding flapping DNS answers with RTT method

I am in the need to understand how GTM metrics work for GTM LDNS probes.   1) how they can be logged the decision? I am using 11.2 but moving fast to 11.4.1.. :)   2) Lets make an example. if...
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  • Cory_50405's avatar
    Cory_50405
    Apr 23, 2014

    The only solution I could see in your situation is to break your single pool into three pools, and either stick with RTT and enable persistence at the wide IP, or switch to topology. Either one should get you some more consistency.

     

Cory_50405's avatar
Cory_50405
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Apr 22, 2014

RTT load balancing is always going to return the answer with the lowest RTT independent of previous results. The amount of time that an answer will remain in an LDNS cache will depend on the TTL you are setting on the GTM. That is if the LDNS respects the TTL, which some do not.

 

If you are looking for more reliability with regards to resolving DNS queries to data centers/servers/etc. within a certain region, you may want to explore topology based load balancing. You can use it to direct users from countries/regions/states to data centers/pools/etc based on geographic location.

 

http://support.f5.com/kb/en-us/products/big-ip_gtm/manuals/product/gtm_config_guide_10_1/gtm_topology_newest.html