Mar 27, 2026 - For details about updated CVE-2025-53521 (BIG-IP APM vulnerability), refer to K000156741.

Implementing Client Subnet DNS Requests

Problem this snippet solves: Update 2018-10-23: As of BIG-IP DNS 14.0 there is now a checkbox feature for edns-client-subnet. Please see: Using Client Subnet in DNS Requests. The following is stil...
Published Jun 16, 2015
BIG-IP DNS
devops
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mchaas's avatar
mchaas
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Aug 31, 2016

Hi,

 

is there a way to tamper with the DNS response based on this information? We are running GTM. When the listener is receiving a DNS query, I would like to decide which virtual server out of the selected pool is used and posted back in the dns response depending on both location (based on the EDNS information) AND availability of the respective resource.

 

So, ideally, in analogy to the GSLB "Topology Record Builder" settings, I would like to set the datacenter information, but not based on the Client-IP in the Layer3 Header, but based on the EDNS client information, as shown in the code snippet.

 

Is this possible? Thanks!

 

Regards, Matt