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George_32239's avatar
George_32239
Icon for Nimbostratus rankNimbostratus
Jul 23, 2012

GTM and Public ISP

Hello,

 

 

I have not seen or played with GTM's so excuse the very likely daft questions !

 

 

so I have public facing web servers. currently they get resolved by public DNS to an IP, that IP hits our firewall and we NAT that IP to the inside IP of the application. Marvellous !, if a little basic.

 

 

So, we are buying a GTM (there will be more than one DC very soon running the same apps)

 

 

so I have an app say;

 

 

thisapp.thisdomain.com resolves via public DNS to public.public.public.public which goes to a particular DC.

 

 

I have seen stuff about adding a CNAME to our DNS (I am assuming public!) and also to add NS records. I guess the GTM will need an IP in the public range that can respond to queries from public DNS's.

 

 

I am not completely clear on what I need to do from an ISP perspective, tell 'em to set up cnames, additonal NS records etc

 

 

If someone has done this before I would be eternally grateful for a set of steps/instructions that perhaps even I could follow !

 

 

Thank you in advance,

 

 

George

 

2 Replies

  • Hamish's avatar
    Hamish
    Icon for Cirrocumulus rankCirrocumulus
    From a high level, you need

     

     

    1. GTM configured to handle a subdomain of your main domain (e.g global.thisdomain.com).

     

    2. A delegation from thisdomain.com for global.thisdomain.com to your GTM servers

     

    3. A configuration in GTM for service.global.thisdomain.com that resolves the IP addresses for you

     

    4. Change the records in your public DNS for service.thisdomain.com to be CNAMEs for service.global.thisdomain.com

     

     

    That's it. There are other ways (e.g. running GTM inline), but I prefer a subdomain. That way you can swap it in & out real easy just by changing the CNAME record in the main DNS...

     

     

    The smarts (and the more involved config) is in the GTM config to resolve service.global.thisdomain.com of course...

     

     

    H
  • The answer is pretty clear,

     

    Now considering i have the website hosted on a server located in the DR site, acting as active/active with the main site host. I think we will be doing the same basic configuration of subdomain and cname for the additional GTM. Usually the GTM can redirect the traffic from one site to another in case of server failure...... However, what happens in case the GTM is down ???? How the ISP will be able to detect the failure of the GTM ??? and would be using only a single GTM without sending any other requests to the failed GTM???? Will the user be able to notice the failure of one of the GTM ??? And for how long will the user still find the website is down ???