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DNS on the internet... how to allow connections?

newbie Marco Nicoloso 2 participants 2 messages Feb 21, 2005 – Feb 22, 2005

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#0 lore raw

Hi there,

I solved all of my routing problems which I had before... Now everything works fine, but the name resolution. According to the scheme (Trusted subnet -> Firewall -> Internet), hosts on my trusted subnet can see the DNS properly, they get its address from the DHCP, but they cannot get DNS queries satisfacted.

I tried with different rules, but none works:
$IPTABLES -A INPUT -p tcp --dport 53 -j ACCEPT
$IPTABLES -A OUTPUT -p tcp --dport 53 -j ACCEPT
$IPTABLES -A INPUT -p udp --dport 53 -j ACCEPT
$IPTABLES -A OUTPUT -p udp --dport 53 -j ACCEPT

or these:
$IPTABLES -A FORWARD -p tcp -s $DNS1_IP -j ACCEPT
$IPTABLES -A FORWARD -p tcp -s $DNS2_IP -j ACCEPT
$IPTABLES -A FORWARD -p udp -s $DNS1_IP -j ACCEPT
$IPTABLES -A FORWARD -p udp -s $DNS2_IP -j ACCEPT

Do I have to setup my own named, cache queries and requests new ones if I need? Or it is just my problem, that I am not able to write rules...?

Thanks in advance

Marco Nicoloso

#1 lore raw

Marco -- yer on the right track -- read in line....

Quoted 7 lines · Marco Nicoloso

Hi there,

I solved all of my routing problems which I had before... Now everything works fine, but the name resolution. According to the scheme (Trusted subnet -> Firewall -> Internet), hosts on my trusted subnet can see the DNS properly, they get its address from the DHCP, but they cannot get DNS queries satisfacted.

DNS queries -- okay - unless the DNS is on the same box as the firewall you
want to :

Quoted 4 lines

I tried with different rules, but none works:
$IPTABLES -A INPUT -p tcp --dport 53 -j ACCEPT
$IPTABLES -A INPUT -p udp --dport 53 -j ACCEPT

Change INPUT to FORWARD
and try again...

Quoted 6 lines

or these:
$IPTABLES -A FORWARD -p tcp -s $DNS1_IP -j ACCEPT
$IPTABLES -A FORWARD -p tcp -s $DNS2_IP -j ACCEPT
$IPTABLES -A FORWARD -p udp -s $DNS1_IP -j ACCEPT
$IPTABLES -A FORWARD -p udp -s $DNS2_IP -j ACCEPT

Loose the above and use an ESTABLISHED, RELATED rule to accept the returns.

Quoted 2 lines

Do I have to setup my own named, cache queries and requests new ones if I need? Or it is just my problem, that I am not able to write rules...?

Nope -- just let the queries THROUGH the firewall -- not in or out.

Alistair

Quoted 4 lines

Thanks in advance

Marco Nicoloso