Q.Can you explain the meaning of following two firewall rules present in my /etc/sysconfig/iptables rules under CentOS Enterprise Linux version 5.2?
-A RH-Firewall-1-INPUT -p 50 -j ACCEPT
-A RH-Firewall-1-INPUT -p 51 -j ACCEPT
I‘m trying to get data (AXFR query) from master tinydns server to secondary DNS server using tcpclient as follows:
tcpclient -v a.ns.example.com 53 axfr-get example.com example.com example.com.tmp
But I’m getting an error which read as follows:
>axfr-get: fatal: unable to parse AXFR results: protocol error
How do I fix this problem?
Q. I run both RHEL / CentOS Linux server and by default firewall blocked out everything including telnet / ssh access. How do I allow telnet – port 23 and ssh port 22 thought Linux iptables firewall ?
A.By default firewall rules stored at /etc/sysconfig/iptables location / file under CentOS / RHEL. All you have to do is modify this file to add rules to open port 22 or 23.
Login as the root user.
Open /etc/sysconfig/iptables file, enter:
# vi /etc/sysconfig/iptables
Find line that read as follows:
To open port 22 (ssh), enter (before COMMIT line):
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT
To open port 23 (telnet), enter (before COMMIT line):
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 23 -j ACCEPT
Save and close the file. Restart the firewall:
# /etc/init.d/iptables restart
I need to disable firewall in Linux for testing purpose. I’m using CentOS and RHEL version 4.4 / 5 / 6. How do I disable the firewall in Linux?
Q. I’d like to start my Iptables based firewall when my computer comes online so that it get protected from the Internet? I’m using CentOS Linux Server version 4.x.
A. CentOS / RHEL / Fedora Linux has service located at /etc/init.d/iptables to start firewall on boot. All you have to do is type the following command to turn on firewall on boot:
# chkconfig iptables on
Your firewall rules are saved at /etc/sysconfig/iptables files.