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krishna_52364's avatar
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Oct 24, 2011

Difference between BIGIP-LTM and BIG-IP GTM




I am new to F5 Load balancing GTM and LTM. I would like to know the difference between LTM and GTM and what they serve for?






5 Replies

  • LTM load balances servers and also does caching, compression, persistence, etc. GTM load balances data centers.



    In a typical deployment, a customer will have 2 data centers, each with GTM and LTM devices. For GTM to work properly, customers delegate DNS resolution to GTM.



    So, a user could type into their browser "" GTM would see the DNS request and see which data center was performing best. If it was data center 1, GTM would return the IP address from the LTM in data center 1. Then, the user would connect to that IP and LTM would load balance the user's request to a server.
  • Hi Chris,



    Another newbie to the GTM - I have a DC in London and just building another in Dublin. We are looking at going down the F5 route and uisng the GTM and the LTM's. Your reply above is very similar to what I want to do and had some questions if you dont mind..



    In your example above, if a user sitting outside of the corporate network enters a URL in their browser or in my case tries to connect to their exchange server over the internet, how do the GTM's deal with this request and load balance it to the DC. Sitting outside the corporate network would mean that I will be using the DNS server allocated to me by my ISP, how will the GTM see that request and which GTM (a pair in each DC) will that request be sent too.



    I guess its all done by delegating the DNS to the GTM and its that bit that I cant seem to understand; your advice will be greatly appreciated or if you have any literature that explains this process will be very useful
  • if GTM act as authoritive DNS, how the client choose to connect which datacenter?


  • This is my hypothesis .. correct me if I'm wrong _/\_



    Assume GTM1 is at DC1 & GTM2 is at DC2


    When Local DNS ask for "" IP at GTM1 (by Default DC) ... GTM 1 in DC 1 will talk with GTM 2 in DC 2 by WAN or else with protocol iQuery.


    to see which data center was performing best. If DC2 is best then GTM 1 will answer Local DNS with A record of "" of DC 2
  • But sounds defeating the purpose, if all requests go to GTM1 and it is the GTM1's job to decide where to send the request, then anything going to DC2 will have extra delay equal to talking to GTM1 and then re-rooted to GTM2 ? It sounds better if there was a separate GTM who's job would be to load balance between two or more DCs without the need for a separate GTM in each DC, just a LTM in each DC.!!!! Am I wrong.???