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Full Discussion: iptables & port 53 (DNS)
Operating Systems Linux Red Hat iptables & port 53 (DNS) Post 302625071 by Duffs22 on Tuesday 17th of April 2012 08:34:24 AM
Old 04-17-2012
iptables & port 53 (DNS)
Hi,

I have a newly built RHEL5 OS that is unable to talk to the DNS server. I am unable to telnet resolv.conf entry over port 53 but apparently this port has been opened.

Code:
# telnet 209.212.96.1 53

and.....

Code:
# dig www.google.com
; <<>> DiG 9.3.6-P1-RedHat-9.3.6-4.P1.el5_4.2 <<>> www.google.com
;; global options: printcmd
;; connection timed out; no servers could be reached

I can only assume therefore that this is a server issue.

So, I have added the following entry to my iptables:

Code:
# iptables -A INPUT -s 41.181.59.124/29 -d 209.212.96.1 -m state --state NEW -m tcp -p tcp --dport 53 -j ACCEPT
 
# iptables -nL
Chain INPUT (policy ACCEPT)
target prot opt source destination 
RH-Firewall-1-INPUT all -- 0.0.0.0/0 0.0.0.0/0 
ACCEPT tcp -- 41.181.59.120/29 0.0.0.0/0 state NEW tcp dpt:53 
ACCEPT tcp -- 41.181.59.120/29 209.212.96.1 state NEW tcp dpt:53

But still unable to telnet to the nameserver over port 53.

Can anybody provide any pointers to what I can try next?

R,
D.
Last edited by Duffs22; 04-17-2012 at 09:42 AM..
 

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LEARN ABOUT MOJAVE

tc-xt

iptables action in tc(8)                                               Linux                                              iptables action in tc(8)

NAME

       xt - tc iptables action

SYNOPSIS

       tc ... action xt -j TARGET [ TARGET_OPTS ]

DESCRIPTION

       The xt action allows to call arbitrary iptables targets for packets matching the filter this action is attached to.

OPTIONS

       -j TARGET [ TARGET_OPTS ]
              Perform a jump to the given iptables target, optionally passing any target specific options in TARGET_OPTS.

EXAMPLES

       The  following  will  attach a u32 filter to the ingress qdisc matching ICMP replies and using the xt action to make the kernel yell 'PONG'
       each time:

              tc qdisc add dev eth0 ingress
              tc filter add dev eth0 parent ffff: proto ip u32 
                   match ip protocol 1 0xff 
                   match ip icmp_type 0 0xff 
                   action xt -j LOG --log-prefix PONG

SEE ALSO

       tc(8), tc-u32(8), iptables-extensions(8)

iproute2                                                            3 Mar 2016                                            iptables action in tc(8)
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