containerization-and-devops

Class 7 - Docker Swarm, Overlay, and Macvlan Networking (Hands-on)

Objective

To initialize Docker Swarm mode correctly on a host with multiple network interfaces
To inspect swarm node status
To create and use an overlay network for container communication
To verify container-to-container connectivity
To inspect host default routing
To create and use a macvlan network with a static container IP

Environment Used

Host OS: Windows
Linux Environment: WSL Ubuntu
Container Platform: Docker Engine
Terminal: WSL Ubuntu

Experiment Execution with Screenshots

Step 1: Initialize Docker Swarm (Error - Multiple IPs)

Command executed:

docker swarm init

Observed error:

Error response from daemon: could not choose an IP address to advertise since this system has multiple addresses on different interfaces (10.255.255.254 on lo and 172.24.124.248 on eth0) - specify one with --advertise-addr

Initialize Docker Swarm Error

Step 2: Initialize Swarm with Advertise Address

Command executed:

docker swarm init --advertise-addr 172.24.124.248

Initialize Swarm with Advertise Address

Step 3: List Swarm Nodes

Command executed:

docker node ls

List Swarm Nodes

Step 4: Create Overlay Network

Command executed:

docker network create -d overlay --attachable my_overlay

Create Overlay Network

Step 5: Run Containers in Overlay Network

Command executed:

docker run -d --network my_overlay --name app1 alpine sleep 3600
docker run -d --network my_overlay --name app2 alpine sleep 3600

Run Containers in Overlay Network

Step 6: Test Connectivity Between Containers

Command executed:

docker exec app1 ping app2

Test Connectivity Between Containers

Step 7: Check Default Route

Command executed:

ip route show default

Check Default Route

Step 8: Create Macvlan Network

Command executed:

docker network create -d macvlan \
  --subnet=172.24.0.0/16 \
  --gateway=172.24.112.1 \
  -o parent=eth0 \
  my_macvlan

Create Macvlan Network

Step 9: Run Nginx Container with Static IP on Macvlan

Command executed:

docker run -d \
  --name web-macvlan \
  --network my_macvlan \
  --ip 172.24.112.50 \
  nginx

Run Nginx on Macvlan

Result

Docker Swarm was successfully initialized using an explicit advertise address. Overlay and macvlan networks were created, containers were deployed, and connectivity/routing checks were validated.

Learning Outcome

Learned why docker swarm init can fail on hosts with multiple interface IPs
Understood how --advertise-addr resolves swarm initialization ambiguity
Practiced creating and using attachable overlay networks
Verified inter-container communication in swarm networking context
Created a macvlan network and assigned a static IP to a container

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