25 Most Frequently Used Linux IPTables Rules Examples
# Modify this file accordingly for your specific requirement. | |
# http://www.thegeekstuff.com | |
# 1. Delete all existing rules | |
iptables -F | |
# 2. Set default chain policies | |
iptables -P INPUT DROP | |
iptables -P FORWARD DROP | |
iptables -P OUTPUT DROP | |
# 3. Block a specific ip-address | |
#BLOCK_THIS_IP="x.x.x.x" | |
#iptables -A INPUT -s "$BLOCK_THIS_IP" -j DROP | |
# 4. Allow ALL incoming SSH | |
iptables -A INPUT -i eth0 -p tcp --dport 22 -m state --state NEW,ESTABLISHED -j ACCEPT | |
iptables -A OUTPUT -o eth0 -p tcp --sport 22 -m state --state ESTABLISHED -j ACCEPT | |
# 5. Allow incoming SSH only from a specific network | |
#iptables -A INPUT -i eth0 -p tcp -s 192.168.200.0/24 --dport 22 -m state --state NEW,ESTABLISHED -j ACCEPT | |
#iptables -A OUTPUT -o eth0 -p tcp --sport 22 -m state --state ESTABLISHED -j ACCEPT | |
# 6. Allow incoming HTTP | |
iptables -A INPUT -i eth0 -p tcp --dport 80 -m state --state NEW,ESTABLISHED -j ACCEPT | |
iptables -A OUTPUT -o eth0 -p tcp --sport 80 -m state --state ESTABLISHED -j ACCEPT | |
# Allow incoming HTTPS | |
iptables -A INPUT -i eth0 -p tcp --dport 443 -m state --state NEW,ESTABLISHED -j ACCEPT | |
iptables -A OUTPUT -o eth0 -p tcp --sport 443 -m state --state ESTABLISHED -j ACCEPT | |
# 7. MultiPorts (Allow incoming SSH, HTTP, and HTTPS) | |
iptables -A INPUT -i eth0 -p tcp -m multiport --dports 22,80,443 -m state --state NEW,ESTABLISHED -j ACCEPT | |
iptables -A OUTPUT -o eth0 -p tcp -m multiport --sports 22,80,443 -m state --state ESTABLISHED -j ACCEPT | |
# 8. Allow outgoing SSH | |
iptables -A OUTPUT -o eth0 -p tcp --dport 22 -m state --state NEW,ESTABLISHED -j ACCEPT | |
iptables -A INPUT -i eth0 -p tcp --sport 22 -m state --state ESTABLISHED -j ACCEPT | |
# 9. Allow outgoing SSH only to a specific network | |
#iptables -A OUTPUT -o eth0 -p tcp -d 192.168.101.0/24 --dport 22 -m state --state NEW,ESTABLISHED -j ACCEPT | |
#iptables -A INPUT -i eth0 -p tcp --sport 22 -m state --state ESTABLISHED -j ACCEPT | |
# 10. Allow outgoing HTTPS | |
iptables -A OUTPUT -o eth0 -p tcp --dport 443 -m state --state NEW,ESTABLISHED -j ACCEPT | |
iptables -A INPUT -i eth0 -p tcp --sport 443 -m state --state ESTABLISHED -j ACCEPT | |
# 11. Load balance incoming HTTPS traffic | |
#iptables -A PREROUTING -i eth0 -p tcp --dport 443 -m state --state NEW -m nth --counter 0 --every 3 --packet 0 -j DNAT --to-destination 192.168.1.101:443 | |
#iptables -A PREROUTING -i eth0 -p tcp --dport 443 -m state --state NEW -m nth --counter 0 --every 3 --packet 1 -j DNAT --to-destination 192.168.1.102:443 | |
#iptables -A PREROUTING -i eth0 -p tcp --dport 443 -m state --state NEW -m nth --counter 0 --every 3 --packet 2 -j DNAT --to-destination 192.168.1.103:443 | |
# 12. Ping from inside to outside | |
iptables -A OUTPUT -p icmp --icmp-type echo-request -j ACCEPT | |
iptables -A INPUT -p icmp --icmp-type echo-reply -j ACCEPT | |
# 13. Ping from outside to inside | |
iptables -A INPUT -p icmp --icmp-type echo-request -j ACCEPT | |
iptables -A OUTPUT -p icmp --icmp-type echo-reply -j ACCEPT | |
# 14. Allow loopback access | |
iptables -A INPUT -i lo -j ACCEPT | |
iptables -A OUTPUT -o lo -j ACCEPT | |
# 15. Allow packets from internal network to reach external network. | |
# if eth1 is connected to external network (internet) | |
# if eth0 is connected to internal network (192.168.1.x) | |
iptables -A FORWARD -i eth0 -o eth1 -j ACCEPT | |
# 16. Allow outbound DNS | |
iptables -A OUTPUT -p udp -o eth0 --dport 53 -j ACCEPT | |
iptables -A INPUT -p udp -i eth0 --sport 53 -j ACCEPT | |
# 17. Allow NIS Connections | |
# rpcinfo -p | grep ypbind ; This port is 853 and 850 | |
#iptables -A INPUT -p tcp --dport 111 -j ACCEPT | |
#iptables -A INPUT -p udp --dport 111 -j ACCEPT | |
#iptables -A INPUT -p tcp --dport 853 -j ACCEPT | |
#iptables -A INPUT -p udp --dport 853 -j ACCEPT | |
#iptables -A INPUT -p tcp --dport 850 -j ACCEPT | |
#iptables -A INPUT -p udp --dport 850 -j ACCEPT | |
# 18. Allow rsync from a specific network | |
#iptables -A INPUT -i eth0 -p tcp -s 192.168.101.0/24 --dport 873 -m state --state NEW,ESTABLISHED -j ACCEPT | |
#iptables -A OUTPUT -o eth0 -p tcp --sport 873 -m state --state ESTABLISHED -j ACCEPT | |
# 19. Allow MySQL connection only from a specific network | |
#iptables -A INPUT -i eth0 -p tcp -s 192.168.200.0/24 --dport 3306 -m state --state NEW,ESTABLISHED -j ACCEPT | |
#iptables -A OUTPUT -o eth0 -p tcp --sport 3306 -m state --state ESTABLISHED -j ACCEPT | |
# 20. Allow Sendmail or Postfix | |
iptables -A INPUT -i eth0 -p tcp --dport 25 -m state --state NEW,ESTABLISHED -j ACCEPT | |
iptables -A OUTPUT -o eth0 -p tcp --sport 25 -m state --state ESTABLISHED -j ACCEPT | |
# 21. Allow IMAP and IMAPS | |
#iptables -A INPUT -i eth0 -p tcp --dport 143 -m state --state NEW,ESTABLISHED -j ACCEPT | |
#iptables -A OUTPUT -o eth0 -p tcp --sport 143 -m state --state ESTABLISHED -j ACCEPT | |
#iptables -A INPUT -i eth0 -p tcp --dport 993 -m state --state NEW,ESTABLISHED -j ACCEPT | |
#iptables -A OUTPUT -o eth0 -p tcp --sport 993 -m state --state ESTABLISHED -j ACCEPT | |
# 22. Allow POP3 and POP3S | |
#iptables -A INPUT -i eth0 -p tcp --dport 110 -m state --state NEW,ESTABLISHED -j ACCEPT | |
#iptables -A OUTPUT -o eth0 -p tcp --sport 110 -m state --state ESTABLISHED -j ACCEPT | |
#iptables -A INPUT -i eth0 -p tcp --dport 995 -m state --state NEW,ESTABLISHED -j ACCEPT | |
#iptables -A OUTPUT -o eth0 -p tcp --sport 995 -m state --state ESTABLISHED -j ACCEPT | |
# 23. Prevent DoS attack | |
iptables -A INPUT -p tcp --dport 80 -m limit --limit 25/minute --limit-burst 100 -j ACCEPT | |
# 24. Port forwarding 422 to 22 | |
#iptables -t nat -A PREROUTING -p tcp -d 192.168.102.37 --dport 422 -j DNAT --to 192.168.102.37:22 | |
#iptables -A INPUT -i eth0 -p tcp --dport 422 -m state --state NEW,ESTABLISHED -j ACCEPT | |
#iptables -A OUTPUT -o eth0 -p tcp --sport 422 -m state --state ESTABLISHED -j ACCEPT | |
# 25. Log dropped packets | |
iptables -N LOGGING | |
iptables -A INPUT -j LOGGING | |
iptables -A LOGGING -m limit --limit 2/min -j LOG --log-prefix "IPTables Packet Dropped: " --log-level 7 | |
iptables -A LOGGING -j DROP |
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