iptables

CentOS

• iptables -A INPUT -p tcp --dport 22 -j ACCEPT
• iptables -A INPUT --protocol tcp --source 192.168.1.0/24 --dport 22 -j ACCEPT
• iptables-save > /etc/sysconfig/iptables

ufw

• ufw allow 22
• ufw allow from 192.168.234.234 to any port 22

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