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santsboy_145140's avatar
santsboy_145140
Icon for Nimbostratus rankNimbostratus
Mar 15, 2014
Solved

GTM and LTM

Hi,

 

we are building twin DCs and we load balance traffic between both Active/Active DCs. I have seen that the best practice is to have in each DC 1 GTM acting as a DNS Server and DC selector and 2 LTM to provide load balancing (I think...).

 

My question is: Will the GTM resolve the DNS to the VIP of the LTMs of the best DC or it will resolve with the IP of the VMs?

 

In case the GTM resolve the DNS to the IP of the VMs, what does the LTM do? (because I though that the LTM selects the DC and the LTM selects the VM).

 

Thank you very much.

 

Regards,

 

JJBN

 

application delivery
BIG-IP DNS
deployment
design
LTM
  • Cory_50405's avatar
    Cory_50405
    Mar 17, 2014

    I hope I answered this in one of your other threads that I commented on. Just to recap, GTM will respond to DNS queries with the virtual server IP address(es) on the LTM. The LTM will be responsible for determining which VM to send the end user traffic to, via whatever health checks and load balancing methods it is configured to use.

     

3 Replies

  • Cory_50405's avatar
    Cory_50405
    Icon for Noctilucent rankNoctilucent
    Mar 17, 2014

    I hope I answered this in one of your other threads that I commented on. Just to recap, GTM will respond to DNS queries with the virtual server IP address(es) on the LTM. The LTM will be responsible for determining which VM to send the end user traffic to, via whatever health checks and load balancing methods it is configured to use.

     

  • cdougall_14195's avatar
    cdougall_14195
    Icon for Cirrus rankCirrus
    Mar 18, 2014

    Please don't think I'm being flippant with my answer, but I'm including a couple of links describing what the two modules are.

    GTM (Performs GSLB): 

    https://f5.com/products/modules/global-traffic-manager
http://support.f5.com/kb/en-us/products/big-ip_gtm/manuals/product/gtm_config_guide_10_1.html

    LTM (Performs Load Balancing)

    https://f5.com/products/modules/local-traffic-manager
http://www.f5.com/pdf/products/big-ip-local-traffic-manager-overview.pdf

    Dig around a bit on the F5 support and look through some of the white papers. Alternatively, it might not be a bad idea to sign up for a couple of the classes they offer with some regularity.

    Cameron Dougall