$ arp -n
$ dig www.google.co.jp
$ dig -x 66.249.89.99
$ dmesg | grep eth0
# echo 0 > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts
# fuser -v -n tcp smtp
$ grep -R eth0 /etc/modprobe.d/
$ grep eth0 /etc/modprobe.conf
$ hostname
$ ifconfig
$ netstat -lp --inet
$ netstat -rn
# nmap -sP -n --send-ip 10.222.1.1-20
# nmap -sS -F -T5 10.222.1.8
# nmap -sU -p 50-55 10.222.1.8
$ nslookup www.google.co.jp
$ ping -b 172.16.255.255
$ route -n
$ sed -n '2p' ~/.ssh/known_hosts | cut -d' ' -f3 | base64 -d | xxd
# service network restart
$ ssh-keygen -l -f ~/.ssh/known_hosts
# sysctl -w net.ipv4.icmp_echo_ignore_broadcasts=0
# tcpdump -i eth0 -s 1500 -X -n
# tcpdump -i eth0 -s 2000 -X -n host 172.16.0.49 and port ssh
$ traceroute www.google.co.jp
$ wget -c --header:REFERER:http://xxx.php http://xxx.zip