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Old 01-20-2012, 02:37 AM   #1
snooze1
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opening ports


i am trying to open a UDP port on Centos 5.7 with iptables.

for some reason "iptables -A INPUT -p udp --dport 7777 -j ACCEPT" isn't working.

any suggestions?
 
Old 01-20-2012, 04:17 AM   #2
aazkan
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Hi

CentOSes up to CentOS 6 uses the RH-Firewall-1-INPUT chain. It goes like this

Code:
-A RH-Firewall-1-INPUT -p udp -m udp --dport 7777 -j ACCEPT
If you have a service or daemon already running on udp port 7777 try connecting to it with nmap or nc like so

Code:
nmap -nv -sU -p 7777 localhost
or

Code:
nc -nvvv -u localhost 7777
Hope this helps.
Regards,

Last edited by aazkan; 01-20-2012 at 04:18 AM. Reason: code tag gets displayed instead
 
Old 01-20-2012, 05:32 AM   #3
snooze1
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Quote:
Originally Posted by aazkan View Post
Hi

CentOSes up to CentOS 6 uses the RH-Firewall-1-INPUT chain. It goes like this

Code:
-A RH-Firewall-1-INPUT -p udp -m udp --dport 7777 -j ACCEPT
If you have a service or daemon already running on udp port 7777 try connecting to it with nmap or nc like so

Code:
nmap -nv -sU -p 7777 localhost
or

Code:
nc -nvvv -u localhost 7777
Hope this helps.
Regards,
And do I add that in /etc/sysconfig/iptables?
 
Old 01-20-2012, 06:35 AM   #4
aazkan
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Yes. Edit /etc/sysconfig/iptables

or if your cli driven (who isn't), as root, type

Code:
iptables -I RH-Firewall-1-INPUT -p --dport 7777 -j ACCEPT
review it like so

Code:
iptables -L -nv |grep 7777
the nmap or nc test can be use as well.
 
Old 01-20-2012, 06:44 AM   #5
snooze1
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Quote:
Originally Posted by aazkan View Post
Yes. Edit /etc/sysconfig/iptables

or if your cli driven (who isn't), as root, type

Code:
iptables -I RH-Firewall-1-INPUT -p --dport 7777 -j ACCEPT
review it like so

Code:
iptables -L -nv |grep 7777
the nmap or nc test can be use as well.
Somehow the port is opened now and I can see the server running fine, but when I try and do it with another server running on 9948 UDP adding "-A RH-Firewall-1-INPUT -p udp -m udp --dport 9948 -j ACCEPT" to the file doesn't work.

Also,

Code:
# iptables -I RH-Firewall-1-INPUT -p --dport 9948 -j ACCEPT
iptables v1.3.5: unknown protocol `--dport' specified
Try `iptables -h' or 'iptables --help' for more information.
 
Old 01-20-2012, 07:06 AM   #6
aazkan
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From you iptables output/example, your're missing

-p udp

Give it another try?
 
Old 01-20-2012, 08:01 AM   #7
snooze1
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Quote:
Originally Posted by aazkan View Post
From you iptables output/example, your're missing

-p udp

Give it another try?
First of all, derp..

Code:
#  iptables -I RH-Firewall-1-INPUT -p udp --dport 9948 -j ACCEPT
iptables: No chain/target/match by that name
 
Old 01-20-2012, 08:21 PM   #8
aazkan
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Then it means there is no such chain. Have a look in your iptables what chains does it use?
 
Old 01-25-2012, 07:23 PM   #9
aazkan
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Hi snooze1,

Thought i chech up with you if you figured out your iptables problem?

tegards,
 
  


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