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I have the following strange problem with the DNS lookups in our Windows domain (dns service runs on the domain controller):

from machine 'A':

  • dns request for machines in the same network zone works
  • dns request for adresses that are not "allowed" result in a timeout / no response

from machine 'B':

  • both lookup requests work

Both machines use the same DNS server

This must mean that:

  • the DNS server knows the correct addresses, and works correctly
  • but: there is some other component (firewall?) in the network that intercepts some DNS requests, based on ckient machine AND request content, and decides to block this request by not returning a response.

This setup forces us to resort to using hostfiles for some connections, since the target machines are reachable.

What could be the reason to configure the network / firewall in such a 'broken' fashion, and what kind of firewall or other appliance has such 'functionallity'?

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  • Define "not allowed" in the context of machine A? Is it specific domains, or every internet domain? The latter would suggest that it is performing lookups against a nameserver that has access to internal DNS data for your network, but not external DNS data.
    – Andrew B
    Oct 19, 2014 at 20:13
  • @AndrewB "not allowed" as in we may not connect to that machine.
    – oɔɯǝɹ
    Oct 19, 2014 at 22:34

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