Bug ID 750472: Certain BIG-IP DNS configurations improperly respond to DNS queries that contain EDNS OPT Records

Last Modified: Jun 30, 2021

Bug Tracker

Affected Product:  See more info
BIG-IP DNS, GTM(all modules)

Known Affected Versions:
11.5.0, 11.5.1, 11.5.1 HF1, 11.5.1 HF10, 11.5.1 HF11, 11.5.1 HF2, 11.5.1 HF3, 11.5.1 HF4, 11.5.1 HF5, 11.5.1 HF6, 11.5.1 HF7, 11.5.1 HF8, 11.5.1 HF9, 11.5.10, 11.5.2, 11.5.2 HF1, 11.5.3, 11.5.3 HF1, 11.5.3 HF2, 11.5.4, 11.5.4 HF1, 11.5.4 HF2, 11.5.4 HF3, 11.5.4 HF4, 11.5.5, 11.5.6, 11.5.7, 11.6.0, 11.6.0 HF1, 11.6.0 HF2, 11.6.0 HF3, 11.6.0 HF4, 11.6.0 HF5, 11.6.0 HF6, 11.6.0 HF7, 11.6.0 HF8, 11.6.1, 11.6.1 HF1, 11.6.1 HF2, 11.6.2, 11.6.2 HF1, 11.6.3,,,, 12.0.0, 12.0.0 HF1, 12.0.0 HF2, 12.0.0 HF3, 12.0.0 HF4, 12.1.0, 12.1.0 HF1, 12.1.0 HF2, 12.1.1, 12.1.1 HF1, 12.1.1 HF2, 12.1.2, 12.1.2 HF1, 12.1.2 HF2, 12.1.3,,,,,,,

Fixed In:
12.1.4,, 11.5.8

Opened: Nov 19, 2018
Severity: 3-Major


DNS Express drops a DNS query that contains an EDNS OPT Record that it does not understand.


DNS Express drops the request. Clients (such as a DNS Flag Day compliance tool) or upstream DNS server will experience a timeout for that query. This is occurring now because of the changes coming that remove certain workarounds on February 1st, 2019. This is known as DNS Flag Day. All network configurations on the internet will be affected by this change, but only some DNS servers will be negatively impacted. Fixes for this issue handle the conditions that were once handled by those workarounds.


If a client (such as a DNS Flag Day compliance tool) or upstream DNS Server sends an invalid ENDS OPT record.



Fix Information

When a query with an invalid EDNS OPT version is received by DNS Express, send a response with the BADVERS error code as stipulated by the RFC. Note: The EDNS Compliance Tester should produce output similar to the following when run against DNS Express: example1.com. @ (ns.example1.com.): dns=ok edns=ok edns1=ok edns@512=ok ednsopt=ok edns1opt=ok do=ok ednsflags=ok optlist=ok signed=ok ednstcp=ok

Behavior Change