Listing 7. Docker adds iptables rules to link containers' ports.

# sudo iptables --list DOCKER
Chain DOCKER (1 references)
target     prot opt source       destination
ACCEPT     tcp  --  anywhere     172.17.0.3   tcp dpt:http
ACCEPT     tcp  --  172.17.0.3   172.17.0.2   tcp dpt:mysql
ACCEPT     tcp  --  172.17.0.2   172.17.0.3   tcp spt:mysql