feat: add network-interface-name-mismatch troubleshooting lab

labs/network-bond-misconfig/cloud-init.yaml

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+#cloud-config
+runcmd:
+  - |
+    # Load dummy module and create an interface named 'ens4'
+    modprobe dummy || true
+    ip link add ens4 type dummy || true
+    ip link set ens4 up
+
+    # Create a Netplan config that refers to 'eth1' instead of 'ens4'
+    cat <<EOF > /etc/netplan/60-internal-nic.yaml
+    network:
+      version: 2
+      renderer: networkd
+      ethernets:
+        eth1:
+          dhcp4: false
+          addresses: [10.10.10.10/24]
+    EOF
+
+    # Try to apply (it will likely complain about missing eth1)
+    netplan apply || true

labs/network-bond-misconfig/lab.yaml

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+id: network-interface-name-mismatch
+name: Network Interface Name Mismatch
+category: networking
+difficulty: intermediate
+vm:
+  name: nic-name-lab
+  image: ubuntu-24.04-base.qcow2
+  memory: 1024
+  cpu: 1
+  disk: 10G
+cloud_init: cloud-init.yaml
+verify_script: verify.sh
+
+description:
+  summary: "The second network interface is down because the configuration refers to a non-existent device name."
+  story: "This server was recently migrated to a new hypervisor. While the primary interface works, the secondary interface (intended for internal traffic) is down. It seems the configuration is looking for 'eth1', but the system has named the hardware differently. You need to find the correct device name and update the configuration."
+  objectives:
+    - Identify the available network interfaces and their states
+    - Locate the incorrect interface name in the Netplan configuration
+    - Update the configuration to use the correct device name and bring the interface up
+tags:
+  - networking
+  - linux
+  - netplan

labs/network-bond-misconfig/question.md

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+### Scenario
+This server was recently migrated to a new virtual environment. While the primary network interface is working fine, the secondary interface, which is supposed to be used for internal database traffic, is not coming up. The previous admin left a Netplan configuration that they claimed should work.
+
+### Objective
+Diagnose why the secondary network interface is down, identify any naming mismatches in the configuration, and restore connectivity on the correct interface with the assigned IP `10.10.10.10`.
+
+### Useful Commands
+- `ip addr`
+- `ip link show`
+- `cat /etc/netplan/60-internal-nic.yaml`
+- `sudo netplan apply`

labs/network-bond-misconfig/solution.md

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+### The Issue
+Modern Linux distributions (especially those using `systemd-networkd` or `Predictable Network Interface Names`) often name network interfaces based on their hardware location (e.g., `ens3`, `enp0s3`) rather than simple indices like `eth0`, `eth1`.
+
+In this case, the Netplan configuration was attempting to configure an interface named `eth1`, but the actual hardware was detected and named `ens4` by the operating system. Because of this mismatch, Netplan could not apply the settings to the correct device, leaving the secondary interface unconfigured.
+
+### Step-by-Step Fix
+
+1. **List all network interfaces**:
+   ```bash
+   ip addr show
+   ```
+   OR
+   ```bash
+   ip link show
+   ```
+   Identify an interface that is `DOWN` or doesn't have an IP, likely named `ens4`.
+
+2. **Inspect the Netplan configuration**:
+   ```bash
+   cat /etc/netplan/60-internal-nic.yaml
+   ```
+   Notice that the configuration block is under `eth1:`.
+
+3. **Correct the interface name**:
+   Edit the file and change `eth1` to `ens4`.
+   ```yaml
+   network:
+     version: 2
+     renderer: networkd
+     ethernets:
+       ens4:
+         dhcp4: false
+         addresses: [10.10.10.10/24]
+   ```
+
+4. **Apply the configuration**:
+   ```bash
+   sudo netplan apply
+   ```
+
+5. **Verify the fix**:
+   Check if `ens4` now has the correct IP address.
+   ```bash
+   ip addr show ens4
+   ```

labs/network-bond-misconfig/solution.sh

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+#!/bin/bash
+
+# Update Netplan configuration to use ens4 instead of eth1
+sed -i 's/eth1:/ens4:/' /etc/netplan/60-internal-nic.yaml
+
+# Apply the new configuration
+netplan apply

labs/network-bond-misconfig/verify.sh

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+#!/bin/bash
+
+# Check if ens4 exists and has the correct IP
+if ip addr show ens4 2>/dev/null | grep -q "10.10.10.10"; then
+    # Also verify it's in Netplan and eth1 is gone
+    if grep -q "ens4:" /etc/netplan/60-internal-nic.yaml && ! grep -q "eth1:" /etc/netplan/60-internal-nic.yaml; then
+        echo "SUCCESS: Secondary interface is correctly configured and up."
+        exit 0
+    else
+        echo "FAILURE: Netplan configuration still refers to eth1 or doesn't have ens4."
+        exit 1
+    fi
+else
+    echo "FAILURE: ens4 does not have the expected IP address 10.10.10.10."
+    exit 1
+fi