cJunosEvolved Lab — Quick Guide

Three Junos routers on Fedora using Containerlab. Works on AMD or Intel.

1. Install Docker and Containerlab

# Docker
sudo dnf install dnf-plugins-core
sudo dnf config-manager addrepo --from-repofile=https://download.docker.com/linux/fedora/docker-ce.repo
sudo dnf install docker-ce docker-ce-cli containerd.io
sudo systemctl enable --now docker

# Containerlab
bash -c "$(curl -sL https://get.containerlab.dev)"

Verify:

docker --version
containerlab version

2. Get the cJunosEvolved image

Download from https://www.juniper.net/us/en/dm/vjunos-labs.html (free, no login). Look for cJunosEvolved-XX.X.X-EVO.tar.gz.

Load it:

sudo docker load -i ~/Downloads/cJunosEvolved-25.4R1.13-EVO.tar.gz
sudo docker images | grep cjunos

Note the exact image tag (e.g. cjunosevolved:25.4R1.13-EVO).

3. Create the topology

mkdir -p ~/junos-lab && cd ~/junos-lab

Save as ~/junos-lab/topology.clab.yml — adjust image: to match your tag:

name: junos-triangle

topology:
  kinds:
    juniper_cjunosevolved:
      image: cjunosevolved:25.4R1.13-EVO

  nodes:
    rt1: { kind: juniper_cjunosevolved }
    rt2: { kind: juniper_cjunosevolved }
    rt3: { kind: juniper_cjunosevolved }

  links:
    - endpoints: ["rt1:et-0/0/0", "rt2:et-0/0/0"]
    - endpoints: ["rt2:et-0/0/1", "rt3:et-0/0/0"]
    - endpoints: ["rt1:et-0/0/1", "rt3:et-0/0/1"]

4. Deploy

cd ~/junos-lab
sudo containerlab deploy -t topology.clab.yml

Wait ~5 minutes for Junos to boot inside each container. Watch one if you want:

sudo docker logs -f clab-junos-triangle-rt1

When you see rt1 login:, it's ready. Ctrl+C to stop following.

5. Connect to a router

Two-step: drop into the container's bash, then telnet to the inner Junos console on port 8601.

sudo docker exec -ti clab-junos-triangle-rt1 bash
# now inside the container:
telnet 127.0.0.1 8601

Press Enter to redraw the prompt. Login as root (blank password). Type cli for the Junos CLI.

Disconnect cleanly:

From Junos CLI back to bash: exit
From telnet: Ctrl-] then type quit
From container bash to host: exit or Ctrl-D

For rt2 use clab-junos-triangle-rt2, for rt3 use clab-junos-triangle-rt3.

6. Daily commands

cd ~/junos-lab

# Boot the lab
sudo containerlab deploy -t topology.clab.yml

# See running state and IPs
sudo containerlab inspect -t topology.clab.yml

# Visual topology graph (browser)
sudo containerlab graph -t topology.clab.yml

# Tear down
sudo containerlab destroy -t topology.clab.yml

inspect only works from inside ~/junos-lab (the topology.clab.yml needs to be findable). Or use sudo containerlab inspect --all from anywhere.

Troubleshooting

Problem	Fix
`Failed to fetch http(s) resource`	You ran the command outside `~/junos-lab`. `cd` there first or use absolute path.
Login prompt doesn't appear	Junos still booting. Wait 5 min total from deploy, mash Enter at the telnet prompt.
`telnet: command not found` inside container	Use `nc 127.0.0.1 8601` instead.
Container not starting	`sudo docker logs clab-junos-triangle-rt1` shows why.
Stuck after Ctrl-C in `docker logs`	That's just stopping the log follow — container is fine.

OSPF working

After applying the OSPF config from Junos_ospf_conf.txt to all three routers and committing, neighbors come up across the triangle and the loopbacks are reachable.

Junos OSPF — neighbor / interface state

Junos OSPF — route table / verification