This is the third part of the series Container Networking. I will explain a little bit about the docker container networking in this blog post. I followed the steps mentioned in this to install docker on Ubuntu. Post docker install, you can see the docker0 device in the list ip link 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000 link/ether 02:fd:4d:34:55:76 brd ff:ff:ff:ff:ff:ff 11: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN mode DEFAULT group default link/ether 02:42:cf:b4:c1:a8 brd ff:ff:ff:ff:ff:ff Let’s create a busybox container. docker run --name bb -dt busybox docker ps -a CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 02429964e449 busybox "sh" About a minute ago Up About a minute bb In the device list, you see the veth7b01920@if16 interface is created with the master as docker0. ip link 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000 link/ether 02:fd:4d:34:55:76 brd ff:ff:ff:ff:ff:ff 11: docker0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default link/ether 02:42:cf:b4:c1:a8 brd ff:ff:ff:ff:ff:ff 17: veth7b01920@if16: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master docker0 state UP mode DEFAULT group default link/ether e2:15:50:88:11:03 brd ff:ff:ff:ff:ff:ff link-netnsid 2 Let’s check the network namespace. ip netns list And you won’t see any network namespaces…How come??? This is because: ip netns list command looks up network namespaces file in the /var/run/netns directory. However, the Docker daemon doesn’t create a reference of the network namespace file in the /var/run/netns directory after the creation. Therefore, ip netns ls cannot resolve the network namespace file Ref: https://www.baeldung.com/linux/docker-network-namespace-invisible If you want ip netns list to show the namespace name docker has created, then follow the below steps export container_name=bb container_pid=$(sudo docker inspect -f '' $container_name) echo $container_pid sudo touch /var/run/netns/$container_name sudo mount -o bind /proc/$container_pid/ns/net /var/run/netns/$container_name Now, you can see the namespace name. ip netns list bb (id: 0) sudo ip netns exec bb ip link 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 16: eth0@if17: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default link/ether 02:42:ac:11:00:02 brd ff:ff:ff:ff:ff:ff link-netnsid 0 The following diagram will help you visualize it better. With this, I’m signing off. I hope this blog series helps to de-clutter container networking. This is the third part of the series Container Networking . I will explain a little bit about the docker container networking in this blog post. Container Networking I followed the steps mentioned in this to install docker on Ubuntu. this Post docker install, you can see the docker0 device in the list docker0 ip link 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000 link/ether 02:fd:4d:34:55:76 brd ff:ff:ff:ff:ff:ff 11: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN mode DEFAULT group default link/ether 02:42:cf:b4:c1:a8 brd ff:ff:ff:ff:ff:ff ip link 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000 link/ether 02:fd:4d:34:55:76 brd ff:ff:ff:ff:ff:ff 11: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN mode DEFAULT group default link/ether 02:42:cf:b4:c1:a8 brd ff:ff:ff:ff:ff:ff Let’s create a busybox container. docker run --name bb -dt busybox docker run --name bb -dt busybox docker ps -a CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 02429964e449 busybox "sh" About a minute ago Up About a minute bb docker ps -a CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 02429964e449 busybox "sh" About a minute ago Up About a minute bb In the device list, you see the veth7b01920@if16 interface is created with the master as docker0. veth7b01920@if16 ip link 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000 link/ether 02:fd:4d:34:55:76 brd ff:ff:ff:ff:ff:ff 11: docker0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default link/ether 02:42:cf:b4:c1:a8 brd ff:ff:ff:ff:ff:ff 17: veth7b01920@if16: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master docker0 state UP mode DEFAULT group default link/ether e2:15:50:88:11:03 brd ff:ff:ff:ff:ff:ff link-netnsid 2 ip link 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000 link/ether 02:fd:4d:34:55:76 brd ff:ff:ff:ff:ff:ff 11: docker0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default link/ether 02:42:cf:b4:c1:a8 brd ff:ff:ff:ff:ff:ff 17: veth7b01920@if16: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master docker0 state UP mode DEFAULT group default link/ether e2:15:50:88:11:03 brd ff:ff:ff:ff:ff:ff link-netnsid 2 Let’s check the network namespace. ip netns list ip netns list And you won’t see any network namespaces…How come??? This is because: ip netns list command looks up network namespaces file in the /var/run/netns directory. However, the Docker daemon doesn’t create a reference of the network namespace file in the /var/run/netns directory after the creation. Therefore, ip netns ls cannot resolve the network namespace file Ref: https://www.baeldung.com/linux/docker-network-namespace-invisible ip netns list command looks up network namespaces file in the /var/run/netns directory. However, the Docker daemon doesn’t create a reference of the network namespace file in the /var/run/netns directory after the creation. Therefore, ip netns ls cannot resolve the network namespace file Ref: https://www.baeldung.com/linux/docker-network-namespace-invisible If you want ip netns list to show the namespace name docker has created, then follow the below steps ip netns list export container_name=bb container_pid=$(sudo docker inspect -f '' $container_name) echo $container_pid sudo touch /var/run/netns/$container_name sudo mount -o bind /proc/$container_pid/ns/net /var/run/netns/$container_name export container_name=bb container_pid=$(sudo docker inspect -f '' $container_name) echo $container_pid sudo touch /var/run/netns/$container_name sudo mount -o bind /proc/$container_pid/ns/net /var/run/netns/$container_name Now, you can see the namespace name. ip netns list bb (id: 0) ip netns list bb (id: 0) sudo ip netns exec bb ip link 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 16: eth0@if17: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default link/ether 02:42:ac:11:00:02 brd ff:ff:ff:ff:ff:ff link-netnsid 0 sudo ip netns exec bb ip link 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 16: eth0@if17: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default link/ether 02:42:ac:11:00:02 brd ff:ff:ff:ff:ff:ff link-netnsid 0 The following diagram will help you visualize it better. With this, I’m signing off. I hope this blog series helps to de-clutter container networking.
