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xdo_217995's avatar
xdo_217995
Icon for Nimbostratus rankNimbostratus
Sep 07, 2015

GTM servers' role

Hi,

 

I'm new to F5 and please bear with me if this question is too naive.

 

I can understand why GTM needs data centers, virtual servers, network, but couldn't get the role of the physical server? Why do we need to create virtual servers under resource for a virtual server? If all virtual servers have to have the same IP as their physical servers, then it makes sense, as for management, the physical server reflects physical condition for a group of virtual servers. Other than that I can't think of any better explanation.

 

Any thoughts on this?

 

BIG-IP DNS

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  • Stanislas_Piro2's avatar
    Stanislas_Piro2
    Icon for Cumulonimbus rankCumulonimbus
    Sep 07, 2015

    Hi,

     

    In GTM (BigIP DNS in version 12.0) :

     

    • a server is a physical object
    • a virtual server is the IP address / port combinaison of the load balanced service

    a server can be :

     

    • a load balancer defined with management IP (F5 LTM, Radware, Cisco).
    • the server hosting multiple virtual hosts with several IPs

    a virtual server can be a load balancer virtual server or a single service on a dedicated server.

     

    if you want to load balance only a service on a server with the same IP, you need to create both server and virtual server with same IP.

     

  • xdo_217995's avatar
    xdo_217995
    Icon for Nimbostratus rankNimbostratus
    Sep 07, 2015

    HI Stanislas,

     

    Thanks for you response. So to recap, correct me if I'm wrong: There are 2 options in using server & virtual server in GTM: 1. Server is LTM (uses mgt IP), virtual servers are LTM virtuals (virtuals IP/port). 2. Server is standalone, virtual server is same server (same IP) + service port.

     

    But that still doesn't explain the needs for physical server. I could create one dummy physical server, and declare all of my virtual servers in resource + service ports (no matter what they are, LTM virtuals or single dedicate servers). Anyway load balancing is done in wideIP logic and in pool you can group any virtual servers you want. So don't see physical server play any role in load balancing job.

     

    Hope I make myself clear here.

     

  • Stanislas_Piro2's avatar
    Stanislas_Piro2
    Icon for Cumulonimbus rankCumulonimbus
    Sep 07, 2015

    There are 2 options in using server & virtual server in GTM:

     

    1. Server is LB (uses Self IP), virtual servers are LB virtuals (virtuals IP/port).
    2. Server is standalone, virtual server is same server (same IP or secondary IP) + service port.

    physical are used for virtual server discovery and monitoring.

     

    When adding a LTM in GTM configuration, all virtual servers are automatically created in GTM. we can disable it if LTM virtual servers address are private and NAT is done by a firewall or router.

     

    Physical server is also used to monitor virtual servers. instead of monitoring all virtual servers, LTM can provide all monitors to GTM in real time.

     

    another goal of LTM servers is to probe LDNS from a datacenter without GTM: In a deployment with more than 2 DC and with one LTM per DC, you can use only 1 GTM in 2 DC and use LTM in other DC to probe LDNS.