📝 Module 2: Version Control with Git

Create a local Git repository on the desktop and make your first commits.

1. Open VS Code and start a terminal:

   Open VS Code via the desktop icon. Then open a terminal via the menu: Terminal → New Terminal (or keyboard shortcut Ctrl+`). A PowerShell terminal appears at the bottom where you can run all Git commands.

   

   🔍 Enlarge

2. Navigate to the desktop and create a folder:
   📄 PowerShell

   📋 Copycd ~\Desktop
   mkdir git-exercise
   cd git-exercise

3. Initialize a Git repository:
   📄 PowerShell

   📋 Copygit init
   
   # Explore the repository
   git status
   
   # Which branch? (should be main or master)
   git branch

4. Open the folder in VS Code and create the first file:

   First, open the created folder in VS Code: File → Open Folder and navigate to Desktop\git-exercise. Click "Select Folder".

   Now you can see the empty folder in the sidebar on the left. Create a new file by clicking the 📄 New File icon in the sidebar (or Ctrl+N) and save the file as vlans.yaml. Enter the following content:

   

   🔍 Enlarge

   📄 vlans.yaml

   📋 Copy# VLAN configuration for my network
   vlans:
     - id: 100
       name: Production
       description: Production servers
   
     - id: 200
       name: Development
       description: Development environment

5. Check status – file is "untracked":
   📄 PowerShell

   📋 Copygit status
   # Untracked files:
   #   vlans.yaml

6. Stage and commit the file:
   📄 PowerShell

   📋 Copygit add vlans.yaml
   git status
   # Changes to be committed:
   #   new file: vlans.yaml (green!)
   
   git commit -m "Added VLAN configuration: Prod + Dev"
   
   # Success message:
   # [main abc1234] Added VLAN configuration: Prod + Dev
   #  1 file changed, 11 insertions(+)

7. View the history:
   📄 PowerShell

   📋 Copygit log --oneline
   git log

Create a feature branch, work in it, and merge it back.

1. Create a new branch:
   📄 PowerShell

   📋 Copy# Create branch AND switch to it
   git checkout -b feature/vlan-300
   
   # Check which branch we are on
   git branch
   # * feature/vlan-300
   #   master

2. Make a change in the new branch:

   Open vlans.yaml in VS Code and add the following at the end:

   📄 vlans.yaml (add at the end)

   📋 Copy
     - id: 300
       name: Guests
       description: Guest network with internet access

3. Commit:
   📄 PowerShell

   📋 Copygit add vlans.yaml
   git commit -m "Added VLAN 300 for guests"

4. Switch back to the master branch and check:
   📄 PowerShell

   📋 Copygit checkout master
   
   # Check: VLAN 300 is NOT here yet!
   Get-Content vlans.yaml

5. Merge the feature branch:
   📄 PowerShell

   📋 Copygit merge feature/vlan-300
   
   # Output:
   # Updating abc1234..def5678
   # Fast-forward
   #  vlans.yaml | 4 ++++
   #  1 file changed, 4 insertions(+)

6. Check the result and clean up:
   📄 PowerShell

   📋 Copy# Now VLAN 300 is also in main!
   Get-Content vlans.yaml
   
   # Log shows the merge
   git log --oneline
   
   # Delete the feature branch
   git branch -d feature/vlan-300

This exercise simulates a real merge conflict – the most important exercise!

1. Make sure you are on master:
   📄 PowerShell

   📋 Copygit checkout master

2. Create Branch A – Alice sets MTU to 9000:
   📄 PowerShell

   📋 Copygit checkout -b feature/mtu-change-alice

   Create a new file interfaces.yaml in VS Code with the following content:

   📄 interfaces.yaml

   📋 Copyinterfaces:
     Ethernet1:
       description: Uplink to Spine
       mtu: 9000

   📄 PowerShell

   📋 Copygit add interfaces.yaml
   git commit -m "Set MTU to 9000 (jumbo frames)"

3. Switch back to master and create Branch B – Bob wants MTU 1500:
   📄 PowerShell

   📋 Copygit checkout master
   git checkout -b feature/mtu-change-bob

   Create the file interfaces.yaml in VS Code (it does not exist on this branch yet!) with the following content:

   📄 interfaces.yaml

   📋 Copyinterfaces:
     Ethernet1:
       description: Uplink to Spine
       mtu: 1500

   📄 PowerShell

   📋 Copygit add interfaces.yaml
   git commit -m "Keep MTU at standard 1500"

4. Merge Alice first (no problem):
   📄 PowerShell

   📋 Copygit checkout master
   git merge feature/mtu-change-alice
   # ✅ Fast-forward, all good

5. Merge Bob → CONFLICT!
   📄 PowerShell

   📋 Copygit merge feature/mtu-change-bob
   
   # 💥 CONFLICT (content): Merge conflict in interfaces.yaml
   # Automatic merge failed; fix conflicts and then commit.
   
   git status
   # both modified: interfaces.yaml

6. View and resolve the conflict:

   Open interfaces.yaml in VS Code. You will see the conflict markers. VS Code offers buttons like "Accept Current Change", "Accept Incoming Change" or "Accept Both Changes". Choose MTU 9000 – remove the conflict markers and keep:

   📄 interfaces.yaml

   📋 Copyinterfaces:
     Ethernet1:
       description: Uplink to Spine
       mtu: 9000

7. Complete the merge:
   📄 PowerShell

   📋 Copygit add interfaces.yaml
   git commit -m "Merge: Keep MTU 9000 (jumbo frames required)"

8. Clean up:
   📄 PowerShell

   📋 Copygit branch -d feature/mtu-change-alice
   git branch -d feature/mtu-change-bob
   
   # View the history with the merge
   git log --oneline --graph --all

Create a project in GitLab and connect your local repository to it.

1. Log into GitLab and create a new project:
   • Open https://198.18.133.100/ in the browser
   • Login with root / C1sco12345
   • Click on "New project" → "Create blank project"
   • Project name: netzwerk-config
   • Deactivate "Initialize repository with a README" (we already have a local repo!)
   • Click on "Create project"
2. Connect local repository with GitLab:
   📄 PowerShell

   📋 Copy# Make sure you are in your local repo
   cd ~\Desktop\git-exercise
   
   # Add GitLab as remote
   git remote add origin https://198.18.133.100/gitlab-instance-668e631e/netzwerk-config.git
   
   # Check if remote is configured
   git remote -v

3. Push local commits to GitLab:
   📄 PowerShell

   📋 Copygit push -u origin master
   
   # On the first push, you will be prompted for username and password:
   # Username: root
   # Password: C1sco12345

4. Verify in GitLab:

   Switch to the browser and reload the project page. You should now see your files (vlans.yaml, interfaces.yaml) and all commits!

Practice the workflow with GitLab: push changes and verify in the browser.

1. Create a new branch and push a change:
   📄 PowerShell

   📋 Copygit checkout -b feature/bgp-config

   Create a new file bgp.yaml in VS Code with the following content:

   📄 bgp.yaml

   📋 Copy# BGP configuration
   bgp:
     local_as: 65001
     router_id: 10.0.0.1
     neighbors:
       - peer: 10.0.0.2
         remote_as: 65002
         description: ISP Uplink

   📄 PowerShell

   📋 Copygit add bgp.yaml
   git commit -m "Added BGP configuration for ISP uplink"
   
   # Push branch to GitLab
   git push -u origin feature/bgp-config

2. Verify in GitLab:
   • Switch to GitLab in the browser
   • In the project, you can now see the branch feature/bgp-config
   • Click on the branch and see the bgp.yaml file
   • Check the history under "Repository → Commits"
3. Switch back to master and merge:
   📄 PowerShell

   📋 Copygit checkout master
   git merge feature/bgp-config
   git push
   
   # Clean up
   git branch -d feature/bgp-config
   git push origin --delete feature/bgp-config

4. Verify in GitLab:

   Reload the project page in GitLab. The bgp.yaml should now be visible in the master branch. The feature branch is deleted.

Create a Merge Request (MR) – the professional way to integrate changes. In real teams, changes are never merged directly, but always through an MR with review.

1. Create a feature branch and make a change:
   📄 PowerShell

   📋 Copygit checkout -b feature/monitoring

   Create a new file monitoring.yaml in VS Code with the following content:

   📄 monitoring.yaml

   📋 Copy# Monitoring configuration
   monitoring:
     snmp:
       community: public
       version: 2c
       targets:
         - 10.0.0.1
         - 10.0.0.2
     syslog:
       server: 10.0.100.50
       port: 514
       level: informational

   📄 PowerShell

   📋 Copygit add monitoring.yaml
   git commit -m "Monitoring configuration: SNMP + Syslog"
   
   # Push branch to GitLab
   git push -u origin feature/monitoring

2. Create a Merge Request in GitLab:
   • Switch to GitLab in the browser
   • GitLab shows a banner at the top: "Create merge request" – click on it
   • Alternatively: In the left menu "Merge requests" → "New merge request"
   • Source Branch: feature/monitoring
   • Target Branch: master
   • Title: Add monitoring configuration
   • Description: Adds SNMP and Syslog monitoring configuration
   • Click on "Create merge request"
3. Review the Merge Request:
   • In the MR, you can see the "Changes" tab – all changes are visible here
   • You can add comments to individual lines (code review!)
   • The "Commits" tab shows all commits in this MR
4. Merge the Merge Request:
   • Click the "Overview" tab at the top
   • Click the blue "Merge" button
   • Optional: Enable "Delete source branch" (recommended!)
   • After the merge, the change is in the master branch
5. Update locally:
   📄 PowerShell

   📋 Copygit checkout master
   git pull
   
   # Check: monitoring.yaml should now be there
   dir
   Get-Content monitoring.yaml
   
   # Clean up the local branch
   git branch -d feature/monitoring