EDNS Compliance Tester

Checking: 'cez.cz.' as at 2025-08-21T17:42:35Z

cez.cz. @89.111.73.200 (ns10.cez.cz.): dns=ok zflag=ok edns=ok edns1=ok edns@512=ok ednsopt=ok edns1opt=ok do=timeout ednsflags=ok docookie=timeout edns512tcp=ok optlist=ok,subnet
cez.cz. @2a01:a040:2004:8100::1 (ns10.cez.cz.): dns=ok zflag=ok edns=ok edns1=ok edns@512=ok ednsopt=ok edns1opt=ok do=timeout ednsflags=ok docookie=timeout edns512tcp=ok optlist=ok,subnet

cez.cz. @89.111.77.200 (ns20.cez.cz.): dns=ok zflag=ok edns=ok edns1=ok edns@512=ok ednsopt=ok edns1opt=ok do=timeout ednsflags=ok docookie=timeout edns512tcp=ok optlist=ok,subnet
cez.cz. @2a01:a040:2004:100::1 (ns20.cez.cz.): dns=ok zflag=ok edns=ok edns1=ok edns@512=ok ednsopt=ok edns1opt=ok do=timeout ednsflags=ok docookie=timeout edns512tcp=ok optlist=ok,subnet

The Following Tests Failed

Warning: test failures may indicate that some DNS clients cannot resolve the zone or will get a unintended answer or resolution will be slower than necessary.

Warning: failure to address issues identified here may make future DNS extensions that you want to use ineffective. In particular echoing back unknown EDNS options and unknown EDNS flags will break future signaling between DNS client and DNS server. We already have examples of this where you cannot depend on the AD flag bit meaning anything in replies because too many DNS servers just echo it back. Similarly the EDNS Client Subnet (ECS) option cannot just be sent to everyone in part because of servers just echoing it back.

• EDNS - DNSSEC (do)

  This is the style of then initial query that BIND 9.1.0 - BIND 9.10.x sends.

  dig +nocookie +norec +noad +dnssec soa zone @server
  expect: SOA
  expect: NOERROR
  expect: OPT record with version set to 0
  expect: DO flag in response if RRSIG is present in response
  See RFC3225

• EDNS - DNSSEC with DNS COOKIE Option (docookie)

  This is the style of the initial query that BIND 9.11.0 and BIND 9.10.4 Windows onwards send.

  dig +cookie +norec +noad +dnssec soa zone @server
  expect: SOA
  expect: NOERROR
  expect: OPT record with version set to 0
  expect: DO flag in response if RRSIG is present in response
  See RFC3225, RFC6891, and RFC7873.

Codes

• ok - test passed.
• subnet - EDNS Client Subnet supported [RFC7871].
• timeout - lookup timed out.

To retrieve this report in the future: https://ednscomp.isc.org/ednscomp/b47c041886

The source code for the tester can be downloaded from ISC Open Source Projects / DNS-Compliance-Testing.

For more information about EDNS please see the main site.

© 2015 Internet Systems Consortium - Powered By: CGIC (License) - Thomas Boutell