How to create a VLAN between two Linux VMs using VxLAN Bridging - TekMonksGitHub/kloudust GitHub Wiki

This guide walks you through the manual commands and example usage for each step. This is useful for Virtual Networks for Tekmonks Kloudust cloud.

1️⃣ Gather Required Information

Before starting, collect the following details:

✅ VLAN Name – A name for your VxLAN (e.g., vxlan100)
✅ VLAN ID – A unique numeric identifier (e.g., 100)
✅ Peer Hosts – IP addresses of other hosts in the VLAN (e.g., 192.168.1.10 192.168.1.11)
✅ Default Ethernet Device – The interface that carries the VxLAN traffic (e.g., eth0)
✅ MTU – Maximum Transmission Unit, typically 1500
✅ Virtual Machine Name (optional) – If you want to attach the VLAN to a VM
✅ Optional Testing Ethernet Pair Name – For testing without a VM (e.g., veth0)

2️⃣ Determine the Default Ethernet Device

If you’re unsure of the default device:

ip route | grep default

Example output:

default via 192.168.1.1 dev eth0

Here, eth0 is the default device.

3️⃣ Set MTU on the Default Ethernet

Set MTU (default is 1500):

sudo ip link set mtu 1500 dev eth0

Example:

sudo ip link set mtu 1500 dev eth0

4️⃣ Create the VxLAN Interface

Create the VxLAN device with the chosen name and ID:

sudo ip link add vxlan100 type vxlan id 100 dev eth0 dstport 0

5️⃣ Add Peer Hosts to the VxLAN

For each peer host IP:

sudo bridge fdb append to 00:00:00:00:00:00 dst 192.168.1.10 dev vxlan100
sudo bridge fdb append to 00:00:00:00:00:00 dst 192.168.1.11 dev vxlan100

6️⃣ Create the Bridge Interface

Create a bridge and attach the VxLAN interface:

sudo ip link add vxlan100_br type bridge vlan_filtering 1
sudo ip link set vxlan100 master vxlan100_br

7️⃣ Bring Up the Interfaces

Bring up the VxLAN and bridge interfaces:

sudo ip link set up dev vxlan100
sudo ip link set up dev vxlan100_br

8️⃣ Configure Firewall to Allow VxLAN Traffic

Open UDP port 8472 (default VxLAN port):

sudo ufw allow proto udp from any to any port 8472
sudo ufw reload

9️⃣ Attach the VLAN to a Virtual Machine (Optional)

If you have a virtual machine named vm1 and want to attach the VLAN bridge to it:

sudo virsh attach-interface --domain vm1 --type bridge --source vxlan100_br --model virtio --config --live

Example:

sudo virsh attach-interface --domain myvm --type bridge --source vxlan100_br --model virtio --config --live

1️⃣0️⃣ Assign an IP to the VM Interface (Inside the VM)

Inside the VM, configure the new network interface (replace enp8s0 with the actual interface name):

sudo ip addr add 10.0.0.10/24 dev enp8s0
sudo ip link set enp8s0 mtu 1450
sudo ip link set up dev enp8s0

1️⃣1️⃣ Testing (Optional)

If you want to test without using a VM, create a virtual Ethernet pair:

sudo ip link add veth0a type veth peer name veth0b
sudo ip link set veth0b master vxlan100_br
sudo bridge vlan add dev veth0b vid 10
sudo ip link set veth0a up
sudo ip link set veth0b up
sudo ip addr add 192.168.10.10/24 dev veth0a

This creates a test environment to validate connectivity.

✅ Done!

You now have:

A VLAN over VxLAN for your VMs
Firewall open for traffic
Optionally attached to VMs or tested with Ethernet pairs