iptables 포트 열기·닫기

iptables (CentOS 6 등)

nmap -p PORT HOST

iptables -A INPUT -p tcp --dport 22 -j ACCEPT    # ssh
iptables -A INPUT -p tcp --dport 80 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j ACCEPT
iptables -A INPUT -p tcp --dport 20 -j ACCEPT    # ftp
iptables -A INPUT -p tcp --dport 21 -j ACCEPT
iptables -A INPUT -p tcp --dport PORT -j DROP

service iptables save
service iptables restart

CentOS 7+ → firewalld firewall-cmd 설정