Iptables simple explanation with exapmles

iptables.md

iptables practice

Check iptables rules

iptables -t {mangle|filter|nat} -L

You can also add the --line-number option to print rules numbers

Delete a rule

iptables -t {mangle|filter|nat} -D CHAIN RULE_NUMBER

Notice that to get the row number you can ues the first command in this gist

Block an incoming packet (icmp)

iptables -t filter -I INPUT -p icmp --icmp-type echo-request -j REJECT

Notice that REJECT returns error, you can use DROP to totally not respond on the request

Block an outcoming packet (icmp)

iptables -t filter -I OUTPUT -p icmp --icmp-type echo-request -j REJECT

Manipulating packet getting out of your system

iptables -t mangle -I POSTROUTING -j TTL --ttl-set 100

Thanks !