I am trying to configure VNC on my server. I found this guide which seems very easy: https://rbgeek.wordpress.com/2012/06/26/how-to-install-vnc-server-on-centos-6/Lastly, I got to iptables configuration:when I run this command as exactly as guide told:sudo iptables -I INPUT 5 -m state --state NEW -m tcp -p tcp -m multiport --dports 5901:5903,6001:6003 -j ACCEPTI terminal throws this message:iptables: Index insertion too bigWhat does it mean? And How can I fix this? 
iptables: Index insertion too big
centos;iptables;vnc
That means that you're trying to insert the rule at a position that doesn't exist in the table.In this case -I INPUT 5 tells iptables to insert the rule on position 5 of the INPUT table but the table is shorter than that.  That guide apparently assumes some pre-existing rules that you don't have.  I looked at it and it doesn't show what they expect.It would most likely be OK to simply skip the 5:sudo iptables -I INPUT -m state --state NEW -m tcp -p tcp -m multiport --dports 5901:5903,6001:6003 -j ACCEPT