If you need to completely reset the firewall rules to a clean, open state, follow the steps below.
Warning: This will remove all existing firewall rules and allow all traffic.
1. Set Default Policies to ACCEPT
This ensures no traffic is blocked after flushing the rules.
iptables -P INPUT ACCEPT
iptables -P FORWARD ACCEPT
iptables -P OUTPUT ACCEPT
2. Flush and Delete All Chains
Removes all existing rules and user-defined chains.
iptables -t nat -F
iptables -t mangle -F
iptables -F
iptables -X
3. Verify Rules
List current rules to confirm they’ve been cleared.
iptables -L -n -v
4. Save the Firewall Changes
Persist the current (empty) configuration.
service iptables save
5. Check NAT Table Output Rules
To view NAT OUTPUT chain details with line numbers:
iptables -t nat -L OUTPUT -n -v --line-numbers
6. Clear IPv6 Firewall Rules (ip6tables)
If IPv6 is enabled, reset those rules as well:
ip6tables -P INPUT ACCEPT
ip6tables -P FORWARD ACCEPT
ip6tables -P OUTPUT ACCEPT
ip6tables -t nat -F
ip6tables -t mangle -F
ip6tables -F
ip6tables -X
7. Verify IPv4 and IPv6 Rules
To confirm everything is cleared:
iptables -L -n -v
ip6tables -L -n -v