Server Fault is a question and answer site for system and network administrators. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

We want to block specific DNS server requests on our network.

We tried null routing the DNS servers that were to be blocked, and it seems DNS requests are still getting through.

Any suggestions welcome.

share|improve this question
...are you sure you're not caching some of the old DNS values on the clients? – Bart Silverstrim Apr 27 '12 at 12:43
Yep, cache cleaned on our test boxes. – notmyname Apr 27 '12 at 12:54
What do you mean block specific DNS servers? Do you mean that you want to block DNS queries to specific DNS servers that users may configure their DNS clients to use? – joeqwerty Apr 27 '12 at 16:20
@joeqwerty - We want to block DNS server requests (port 53). Yes. – notmyname May 1 '12 at 18:59
up vote 9 down vote accepted

Best bet is to block the DNS server IP at your firewall. That would stop any and all requests for sure.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.