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
Version 1.0
BIG-IP DNS
devops
iRules
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StephanManthey
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Dec 18, 2019

In service request C3152801 the F5 support confirmed a bug (ID832769: [DNS::edns0 subnet address] printing random octets when edns client subnet mask is /24 or lower) for TMOS v12 which is fixed in TMOS v14.

In case you are using DNS::return in your TMOS v12 iRule, the EDNS0-ECS information will be inserted automatically. So there is no need to insert this information in the context of DNS_RESPONSE.

But in case the request is handled by gtmd or bind you will need to insert the EDNS0-ECS information the DNS_RESPONSE context.

TMOS v14 has changes in behaviour and fixes. In case you are upgrading, review your iRules, please.