How to make VLAN configuration permanent?

To make VLAN configuration permanent on a Linux system, you typically need to edit the network configuration files. The exact method can vary depending on the distribution you are using. Below are examples for both Debian-based and Red Hat-based systems.

For Debian-based systems (like Ubuntu):

Edit the interfaces file: Open the /etc/network/interfaces file in a text editor:
```
sudo nano /etc/network/interfaces
```
Add VLAN configuration: Add the following lines, replacing eth0 with your actual interface name and 10 with your VLAN ID:
```
auto eth0.10
iface eth0.10 inet dhcp
```
This configuration will create a VLAN interface eth0.10 that uses DHCP.
Restart networking: After saving the file, restart the networking service:
```
sudo systemctl restart networking
```

For Red Hat-based systems (like CentOS):

Create a VLAN configuration file: Create a new file in the /etc/sysconfig/network-scripts/ directory. The filename should be in the format ifcfg-ethX.Y, where X is the interface number and Y is the VLAN ID. For example:
```
sudo nano /etc/sysconfig/network-scripts/ifcfg-eth0.10
```
Add VLAN configuration: Add the following lines to the file:
```
DEVICE=eth0.10
BOOTPROTO=dhcp
VLAN=yes
```
Restart networking: Restart the network service to apply the changes:
```
sudo systemctl restart network
```

Verification

You can verify that the VLAN is configured correctly by using the following command:

ip link show

This will list all network interfaces, including your newly created VLAN interface.