Set the default policies for all chains to ACCEPT:
sudo iptables -P INPUT ACCEPT
sudo iptables -P FORWARD ACCEPT
sudo iptables -P OUTPUT ACCEPT
Flush all rules from the filter table:
sudo iptables -F
Remove any user-defined chains:
sudo iptables -X
Flush rules from other tables (nat, mangle, raw) to ensure a complete reset:
sudo iptables -t nat -F
sudo iptables -t mangle -F
sudo iptables -t raw -F
Remove user-defined chains from other tables:
sudo iptables -t nat -X
sudo iptables -t mangle -X
sudo iptables -t raw -X