[CentOS] Iptables not blocking UDP port 53

Johnny Hughes jhughes at hughesjr.com
Sat Jul 12 00:03:36 UTC 2008

Sean Carolan wrote:
> I'm attempting to block access to port 53 from internet hosts for an
> internal server.  This device is behind a gateway router so all
> traffic appears to come from source ip  Here are my
> (non-working) iptables rules:

If it is behind a gateway router, how is port 53 traffic getting from 
the internet to that DNS server in the first place.

Also ... IF you are PORT FORWARDING port 53 from the internet to the DNS 
server, then the SOURCE IP will not be the IP of the forwarding device, 
but the IP of the machine making the request.

If this device is really behind a firewall why are you even forwarding 
any traffic to it from port 53 in the first palce?

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