Hi David,

From the Network -> Firewall tab

Deny LAN->EXT TCP/UDP 0/0 0/0 53

<<inline: dns.jpg>>


This applies for both IPv4 and IPv6 if enabled.  TCP is seldom used, but best 
to also block it.


Now for the extra credit, :-), this can't be done via the Firewall tab, but if 
you also add the AIF variable to your user.conf:

LAN_INET_HOST_OPEN_UDP="0/0>208.67.222.222~53 0/0>208.67.220.220~53"

That will allow the LAN to directly access the OpenDNS IPv4 servers with the 
Firewall tab rule applied, (also define LAN_INET_HOST_OPEN_TCP the same if you 
wish). IMHO not worth the effort, why not force all LAN users to use the local 
cacheing DNS server.

Lonnie


On Jul 15, 2012, at 4:01 PM, David Kerr wrote:

> So, the OpenDNS was mentioned on this list a few days ago.  I use this 
> service and the mention on this list prompted me to check my settings to make 
> sure that I was still appropriately blocking access to web site categories.  
> And it started me thinking... it would be easy for a savvy user to 
> reconfigure their client DNS settings such that it no longer pointed to 
> 192.168.1.1 (or whatever AstLinux is on your network, or whavever DHCP 
> returned_) and instead pointed to a public DNS server, maybe my ISP's DNS 
> server. 
> 
> So... is there a way to configure the AstLinux firewall to block DNS requests 
> from any internal client to any external DNS server?  In other words, enforce 
> internal clients to use the AstLinux DNS server.  For extra credit... a rule 
> that would never-the-less permit access to the OpenDNS servers 208.67.222.222 
> and 208.67.220.220.
> 
> Thanks,
> David



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