Docker: Two containers under same network cann't communicate - docker

Question

I created two docker containers and connected them to the same network, but either of the container cannot connect to the other one.
I have tried the steps on this page, but none of the methods worked.
Anything else I can try?
docker run -d --name db1 -e POSTGRES_PASSWORD=password postgres:10-alpine
docker run -d --name db2 -e POSTGRES_PASSWORD=password postgres:10-alpine
docker network create myNetwork
docker network connect myNetwork db1
docker network connect myNetwork db2
# make sure that the network has 2 containers
docker inspect myNetwork
docker exec -it db1 ping db2
PING db2 (172.18.0.4): 56 data bytes
^C
--- cvat_db ping statistics ---
3 packets transmitted, 0 packets received, 100% packet loss
docker exec -it db1route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
default 172.18.0.1 0.0.0.0 UG 0 0 0 eth0
172.18.0.0 * 255.255.0.0 U 0 0 0 eth0
#ifconfig
br-3f4022544f42: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 172.18.0.1 netmask 255.255.0.0 broadcast 172.18.255.255
inet6 fe80::42:e5ff:fe9f:33bc prefixlen 64 scopeid 0x20<link>
ether 02:42:e5:9f:33:bc txqueuelen 0 (Ethernet)
RX packets 21 bytes 1164 (1.1 KB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 44 bytes 5656 (5.6 KB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
docker0: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500
inet 172.17.0.1 netmask 255.255.0.0 broadcast 172.17.255.255
inet6 fe80::42:b9ff:fe47:f00c prefixlen 64 scopeid 0x20<link>
ether 02:42:b9:47:f0:0c txqueuelen 0 (Ethernet)
RX packets 1 bytes 28 (28.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 54 bytes 6637 (6.6 KB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0