DevOps Classroom Series – 28/Jun/2020

Docker Networking

• References: Networking-1, Swarm, Networking-2

• Docker containter network architecutre is built on set of interfaces/rules called as Container Networking Model (CNM)

• CNM Constructs:

  1. Sandbox: this is containers network stack with features such as container network interfaces, routing tables and DNS settings
  2. Endpoint: joins sandbox to network
  3. Network: Network is collection of endpoints with connectivity b/w them.

• CNM Driver Interfaces

• CNM provides two pluggable and open interfaces

  • Network Driver
  • IPAM (IP Addresss Managment) Drivers

• Native Network Drivers: docker has a section for network docker network

• Docker native network drivers:

  • Host: with host driver , a container uses the networking stack of host.
  • Bridge: This is default driver. Connecting multiple containers on the same bridge network in a single host. The containers created by default are connected to bridge network
  • Overlay: This driver creates an overlay network to support multi-host containers.
  • MACVLAN:
  • None

• Lets experiment.

  • Create a nginx container and execute docker inspect <container-id>
  • now lets inspect bridge network docker network inspect bridge

Bridge Network

• In docker by default we will have a default bridge network with name bridge.
• Lets create a new bridge (user-defined bridge)

docker network create --help
docker network create --driver bridge --subnet 10.10.0.0/24 mybridge

• So lets create two container inside mybridge network

docker container run -d --name c1 --network mybridge alpine sleep 1d
docker container run -d --name c2 --network mybridge alpine sleep 1d

• Lets find the ipaddress of the contianer

docker network inspect mybridge

• Lets ping between container by name and ipaddress

docker container exec c1 ping -c 4 c2
docker container exec c1 ping -c 4 10.10.0.3

Docker Swarm

• Docker swarm is docker native orchestration tool which helps in running containers on multi hosts.

• In the below image assume we have mulitple hosts running containers on their bridge network.

• Communications between containers on same host are possible but not on multi-hosts

• In Docker swarm all the machines are referred as nodes. There are two kinds of nodes

  1. Manager node(s)
  2. worker nodes

• Lets create docker swarm by following steps mentioned over here in the swarm setup

• Service, task and container

• Lets create a service to run 3 replicas of httpd in swarm manager

docker service create --replicas 2 --name httpd httpd 

• scale the containers
• create a docker service with ports exposed docker service create --name httpd --replicas 2 --update-delay 10s --publish published=8081,target=80 httpd

Networking in Windows Server

• Default driver is NAT (equivalent to bridge)
• Transperent driver is equivalent to host driver