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At work we use OpenDNS and it has wrongly blocked irc.freenode.net for malware. How can I make sure that any request for *.freenode.net goes to 8.8.8.8 and 8.8.4.4 (Google's DNS).

I tried doing this by fiddling with resolv.conf on Ubuntu, but I wasn't able to get too far. Also, is there an easy way to do this for Mac and Windows systems (I have a few colleagues using those OSes and they'd like to use IRC as well).

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Be careful - attempting to get around security controls can get one escorted out of some companies. Also, it is possible other DNS servers are blocked. –  uSlackr May 23 '12 at 17:09
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2 Answers 2

up vote 4 down vote accepted

Linux does not support the use of domain-specific DNS servers via resolv.conf. You could potentially work around this by running a caching nameserver (such as BIND or dnsmasq) locally and then configuring explicit forwarders for each domain.

Under OS X, this sort of setting is relatively easy using the scutil command. The common use case for this configuration is to forward DNS requests for a VPN connection to VPN-specific DNS servers, so you'll find this discussed often in concert with, e.g., OpenVPN. This document talks about the scutil command as does this, and a Google search for openvpn and scutil will yield more results.

I'm not sure about Windows. You could presumably use the local DNS server solution for all three platforms if you needed to.

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This can't be done with the standard DNS resolution provided by *nix (and Windows AFAIK), you need your own DNS server to do this. On *nix dnsmasq is the best choice for this, and you can either run this on every workstation or run it on a server and configure all the workstations to use this.

/etc/resolv.conf:

nameserver 127.0.0.1
nameserver 208.67.222.222
nameserver 208.67.220.220

/etc/dnsmasq.conf:

server=/freenode.net/8.8.8.8
server=/freenode.net/8.8.4.4
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This can absolutely be done using the standard DNS resolution provided by some operating systems. Just not by Linux. –  larsks May 23 '12 at 17:00
    
Thanks, clarified. –  mgorven May 23 '12 at 17:03
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