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telnet to 53

Posted on 2008-11-11
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Last Modified: 2013-12-16
Hi, i have configured my server as Dns.

now I have changed others pc to look at the dns server by editing /etc/resolv.conf .
Everything is fine, internal pc can resolve anything via my dns server.
but one thing is wired.

if try to telnet to 53 port of my server it will say connection refused.
now i have added to allow any connection to come to port 53 [ hense, all internal pc can resolv any ip via my dns server] but still if i try to telnet to dns server it will not work.

now : if flush iptables then it will allow to telnet. so its iptables issue.
but I dont understand, i have opend port 53 still why i am not able to telnet port 53 ?

I have attached my iptables -L here  [ yo will seee the before last line, i have addedd trafiq to allow port 53]

[root@workshop setroubleshoot]# iptables -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination
RH-Firewall-1-INPUT  all  --  anywhere             anywhere
 
Chain FORWARD (policy ACCEPT)
target     prot opt source               destination
RH-Firewall-1-INPUT  all  --  anywhere             anywhere
 
Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination
 
Chain RH-Firewall-1-INPUT (2 references)
target     prot opt source               destination
ACCEPT     all  --  anywhere             anywhere
ACCEPT     icmp --  anywhere             anywhere            icmp any
ACCEPT     esp  --  anywhere             anywhere
ACCEPT     ah   --  anywhere             anywhere
ACCEPT     udp  --  anywhere             224.0.0.251         udp dpt:mdns
ACCEPT     udp  --  anywhere             anywhere            udp dpt:ipp
ACCEPT     tcp  --  anywhere             anywhere            tcp dpt:ipp
ACCEPT     all  --  anywhere             anywhere            state RELATED,ESTAB                                                                                                  LISHED
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:n                                                                                                  fs
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:s                                                                                                  sh
ACCEPT     udp  --  anywhere             anywhere            state NEW udp dpt:n                                                                                                  etbios-ns
ACCEPT     udp  --  anywhere             anywhere            state NEW udp dpt:n                                                                                                  etbios-dgm
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:n                                                                                                  etbios-ssn
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:m                                                                                                  icrosoft-ds
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:h                                                                                                  ttp
ACCEPT     udp  --  anywhere             anywhere            state NEW udp dpt:d                                                                                                  omain
REJECT     all  --  anywhere             anywhere            reject-with icmp-ho                                                                                                  st-prohibited

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Question by:fosiul01
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by:http:// thevpn.guru
ID: 22928803
Are using tcp on DNS or UDP

netstat -an | grep :53
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by:fosiul01
ID: 22928821
Hellooooooooooo boSS
after long time!! i emailed you soo many times about " how are u"" ok no problem,

i added rule as Udp ,

I didnot think i need to add tcp aswell

shall i add tcp ??


[root@workshop setroubleshoot]# netstat -an | grep :53
tcp        0      0 192.168.2.116:53            0.0.0.0:*                   LISTEN
tcp        0      0 127.0.0.1:53                0.0.0.0:*                   LISTEN
udp        0      0 0.0.0.0:53                  0.0.0.0:*                      
udp        0      0 192.168.2.116:53            0.0.0.0:*                      
udp        0      0 127.0.0.1:53                0.0.0.0:*                      
udp        0      0 0.0.0.0:5353                0.0.0.0:*                      
udp        0      0 :::53                       :::*                            
udp        0      0 :::5353                     :::*            
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http:// thevpn.guru earned 1800 total points
ID: 22928827
Yeah add tcp as well...hehe thanks I am fine but VERY busy.
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Author Comment

by:fosiul01
ID: 22928842
hahahaah yap  done

i have added tcp and its able to telnet

but adding tcp is not manditory, right ??

whats the relation between telnet to 53  and tcp ??
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Assisted Solution

by:Tintin
Tintin earned 200 total points
ID: 22928852
You can't telnet to UDP services.
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Expert Comment

by:http:// thevpn.guru
ID: 22928868
as @Tintin said UDP is stateless I.e. you can not establish a 3 way handshake and have a telnet connection.
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