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Senthilko_37896's avatar
Senthilko_37896
Icon for Nimbostratus rankNimbostratus
Dec 11, 2018

What Happens if you do a DNS lookup on GTM FQDN ?

Hey There !! Totally new to Load Balancing here. We do have GTM/LTM configured for our Web Servers with one GTM pooling 2 LTM'S (for each DC) .If we do a DNS lookup on the GTM FQDN (nslookup FQDN) it gives the LTM1 IP the first time and LTM2 IP the second time ( which is fine due to the Robin Robin Algorithm).

 

Question here is....I always thought that the GTM FQDN will resolve to its own IP like a GTM VIP that in turn delegates to its two LTM's. But it is not. When we do a DNS lookup it just delegates to the LTM IP's. So what is my misunderstanding here ?? GTM does not have an IP by itself ? rather it just delegates to the LTM's ?

 

Thanks in Advance

 

application delivery
BIG-IP
BIG-IP DNS
security

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  • nathe's avatar
    nathe
    Icon for Cirrocumulus rankCirrocumulus
    Dec 11, 2018

    Senthilko,

     

    GTM can be configured in many ways. With GSLB and Wide IPs then GTM just has a zone delegated to it and Wide IPs - this responds to a DNS lookup with an IP address which is sourced from a WideIP pool member i.e. LTM VIP.

     

    GTM can also be a secondary DNS server or replace/be in front of existing DNS servers. See the implementation guide as I'm sure this will help DNS Implementations

     

    Hope this helps,

     

    N