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Editorial Team
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Asked: 2026-05-16T21:54:37+00:00

I’m trying to configure my server to allow incoming DNS queries. The default server,

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I’m trying to configure my server to allow incoming DNS queries. The default server, as setup by the hosting company, permits traffic on ports 443, 80 and 22.

I have modified the iptables file to try to permit requests on port 53, but I am not getting any response from BIND. Turning off the firewall permits the DNS request to go through, so that suggests to me that the nameserver is working correctly. The setup is CentOS 5.5.

This is the iptables file; I’d appreciate it if someone could tell me what I’m missing here in order to get this working.

Thanks in advance.

==================

# Firewall configuration written by system-config-securitylevel
# Manual customization of this file is not recommended.
*filter
:FORWARD ACCEPT [0:0]
:INPUT ACCEPT [0:0]
:RH-Firewall-1-INPUT - [0:0]
:OUTPUT ACCEPT [0:0]
-A INPUT -j RH-Firewall-1-INPUT
-A FORWARD -j RH-Firewall-1-INPUT
-A RH-Firewall-1-INPUT -i lo -j ACCEPT
-A RH-Firewall-1-INPUT -p icmp --icmp-type any -j ACCEPT
-A RH-Firewall-1-INPUT -p 50 -j ACCEPT
-A RH-Firewall-1-INPUT -p 51 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp -d 224.0.0.251 --dport 5353 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp -m udp --dport 631 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m tcp --dport 631 -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m state -m tcp --dport 10000 --state NEW -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m tcp --dport 1024:65535 --sport 53 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp -m udp --dport 1024:65535 --sport 53 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m state -m tcp --dport 22 --state NEW -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m state -m tcp --dport 80 --state NEW -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m state -m tcp --dport 443 --state NEW -j ACCEPT
-A RH-Firewall-1-INPUT -j REJECT --reject-with icmp-host-prohibited
COMMIT
# Generated by webmin
*mangle
:FORWARD ACCEPT [0:0]
:INPUT ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
:PREROUTING ACCEPT [0:0]
:POSTROUTING ACCEPT [0:0]
COMMIT
# Completed
# Generated by webmin
*nat
:OUTPUT ACCEPT [0:0]
:PREROUTING ACCEPT [0:0]
:POSTROUTING ACCEPT [0:0]
COMMIT
# Completed
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1 Answer

  1. Editorial Team

    This line from your rules is completely wrong:

    -A RH-Firewall-1-INPUT -p tcp -m tcp --dport 1024:65535 --sport 53 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp -m udp --dport 1024:65535 --sport 53 -j ACCEPT

    You’re saying: allow traffic from remote port 53 to local ports 1024 – 65535.
    I believe DNS is listening on port 53. Try this instead (allow every TCP/UDP traffic to destination port 53):

    -A RH-Firewall-1-INPUT -p tcp --dport 53 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp --dport 53 -j ACCEPT

    These lines won’t do anything:
    The following lines allows traffic with the protocol number 50 (ESP) and 51 (AH) (source: IANA Protocol Numbers)

    -A RH-Firewall-1-INPUT -p 50 -j ACCEPT
-A RH-Firewall-1-INPUT -p 51 -j ACCEPT
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