I am using Ubuntu 12.04 . while learning some new things about iptables i cant through this . see at the image . while i am trying to start ,its saying as root@badfox:~# iptables -L -n -v Chain INPUT (policy ACCEPT 0 packets, 0 bytes) pkts bytes target prot opt in out source destination Chain FORWARD (policy ACCEPT 0 packets, 0 bytes) pkts bytes target prot opt in out source destination Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes) pkts bytes target prot opt in out source destination root@badfox:~# service iptables stop iptables: unrecognized service root@badfox:~# service iptables start iptables: unrecognized service Source: http://www.cyberciti.biz/tips/linux-iptables-examples.html Why i am getting like this ? EDIT: So my firewall already started but why i am not getting the output as i mentioned in the link at source link in first workout. . Here is my output root@badfox:~# sudo start ufw start: Job is already running: ufw root@badfox:~# iptables -L -n -v Chain INPUT (policy ACCEPT 4882 packets, 2486K bytes) pkts bytes target prot opt in out source destination Chain FORWARD (policy ACCEPT 0 packets, 0 bytes) pkts bytes target prot opt in out source destination Chain OUTPUT (policy ACCEPT 5500 packets, 873K bytes) pkts bytes target prot opt in out source destination root@badfox:~#