No network access between docker container A and B

Question

I have started two simple docker containers using docker-compose. Each container can access the host machine, the host machine can access each container, but the containers cannot access each other.

They are given IP address 172.19.0.2 and 172.19.0.3 so they are on the same bridge.

nmap shows up the ports as filtered.

What is wrong in my setup?

Edit:

$ brctl show
bridge name     bridge id               STP enabled     interfaces
br-48718423616d         8000.0242ee6d819b       no
br-9b06de56c2e7         8000.0242f86db034       no              veth4c40427
                                                        vethf7f18db
docker0         8000.0242a8db6939       no
$ bridge link
7: vethf7f18db@if6: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 master br-9b06de56c2e7 state forwarding priority 32 cost 2
9: veth4c40427@if8: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 master br-9b06de56c2e7 state forwarding priority 32 cost 2

Answer 1

The host needs to allow IP forwarding.

So try iptables -P FORWARD ACCEPT on the host machine.