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Ben__135755's avatar
Ben__135755
Icon for Nimbostratus rankNimbostratus
Jul 07, 2014

Split DNS for GTM published Wide IPs for LTM VSs

I am using an F5 device running BIG-IP 11.4.1

 

I am trying to configure GTM to provide either an external ip or an internal ip for the same dns request depending on the source of the request. I understand I do this with the topology records.

 

My problem is that to publish my site internally and externally I have two separate LTM virtual servers. Both are attached to different private ip addresses. The externally published site can be reached because of a NAT configured to route between the public ip and its private ip. I am getting GTM to use Virtual Server Discovery, in order to discover my LTM virtual servers.

 

GTM successfully distributes different IP addresses depending on the source of the DNS request, however because my 'external' LTM virual server is listening on a private address, this private address is distributed rather than the public address that I need external requesters to receive.

 

Is there a way that I can configure the LTM (perhaps with a NAT) to ensure that GTM hands out a public ip address for my external LTM virtual server? If I configure my LTM virtual server with the external IP and set up a NAT on the F5, the correct IP is handed out but the site is not accessible (presumably as the device is not actually listening on the public ip but instead it is NAT'd through to the internal ip).

 

Let me know if there is any of the config that is unclear. Thanks

 

application delivery
BIG-IP DNS
design
LTM

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  • James_Thomson's avatar
    James_Thomson
    Icon for Employee rankEmployee
    Jul 08, 2014

    Can you give an example with IP addresses? I'm not sure I quite follow you. There is a feature in GTM when configuring a virtual server which has a private IP address, you can configure a "translation address". So, autodiscover finds the real "internal" IP address, then you need to go in and edit the virtual server and give it the "translation address" which GTM will then hand out.

     

    I think that may be what you need, but not sure. Maybe this helps:

     

    http://support.f5.com/kb/en-us/solutions/public/14000/700/sol14707.html

     

    • _lt_--kb--_gt__'s avatar
      _lt_--kb--_gt__
      Icon for Nimbostratus rankNimbostratus
      Jun 30, 2016
      I accomplished this by disabling virtual server discovery and manually creating the virtual server under GSLB. You can then enter the public address as "Address" and the real address on the VIP as "Translation". Works well.