How to configure 802.1Q VLAN Tagging on Debian 9

Estimated reading time: 2 min

Introduction

VLANs make it possible to separate large networks into smaller and manageable ones. The 802.1Q is a standard which is implemented by all vendors into their network equipment. Some switches have the ability to assign multiple VLANs to a single network port. With this feature, you can assign multiple VLANs to a single server. The switch can separate the packages because every Ethernet frame is tagged with the VLA

Prerequisites

  • The network switch your server is connected to must be set up for a successful procedure
  • The switch should support VLAN tagging
  • You must be logged in via SSH as sudo or root user. This tutorial assumes that you are logged in as a sudo user.

Step 1 – Log in using SSH

You must be logged in via SSH as sudo or root user. Please view this article for instructions if you don’t know how to connect.

Step 2 –  Install dependency

sudo apt-get install vlan

Step 3 –  Create network routes

Edit the following file in order to allow multiple VLANs on your server to create routing tables. 

sudo nano /etc/iproute2/rt_tables

Add the following lines.

500    firsttable
501    secondtable

Step 4 – Find the active network interface

clear && echo $(ip -o -4 route get 8.8.8.8 | sed -nr 's/.*dev ([^\ ]+).*/\1/p')

Step 5 –  Configure the network interface

In our example our network interface is eth0. Our article will use eth0 but you have to use the network interface name from step 4.

Edit your network configuration.

sudo nano /etc/network/interfaces

Remove the following lines.

# The primary network interface
allow-hotplug eth0
iface eth0 inet static
        address 89.207.131.20/24
        gateway 89.207.131.1
        # dns-* options are implemented by the resolvconf package, if installed
        dns-nameservers 89.207.128.252 89.207.130.252
        dns-search snel.com

Configure the first VLAN 453.

auto eth0.453
iface eth0.453 inet static
    address 89.207.131.20
    netmask 255.255.255.0
    gateway 89.207.131.1
    dns-nameservers 89.207.128.252 89.207.130.252 
    dns-search snel.com    

Configure the second VLAN 3047.

auto eth0.3047
iface eth0.3047 inet static
    address 78.41.207.45
    netmask 255.255.255.0
    post-up ip route add 78.41.207.0/24 dev eth0.3047 src 78.41.207.45 table secondtable
    post-up ip route add default via 78.41.207.1 dev eth0.3047 table secondtable
    post-up ip rule add from 78.41.207.0/24 table secondtable
    post-up ip rule add to 78.41.207.0/24 table secondtable

Step 6 – Configure sysctl

Enable packet forwarding on the server by creating the following file.

sudo nano /etc/sysctl.d/90-override.conf

Add the following line.

net.ipv4.ip_forward=1

Enable reverse path and arp filtering.

net.ipv4.conf.all.arp_filter=0
net.ipv4.conf.all.rp_filter=2

Apply the changes.

sudo sysctl -p /etc/sysctl.d/90-override.conf

Step 7 – Restart the server

sudo reboot

Step 8 – Test IP addresses

Ping from your workstation to check if the IPs are active.

ping 78.41.207.45
ping 89.207.131.20

Step 9 – Test IP address on Server

Check if the packets are using the right VLAN to leave the server

Perform a ping from eth0.3047 to check if it’s using the right VLAN to communicate with the destination IP address.

ping -I eth0.3047 8.8.8.8

Output

PING 8.8.8.8 (8.8.8.8) from 78.41.207.45 eth0.3047: 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=122 time=2.03 ms
64 bytes from 8.8.8.8: icmp_seq=2 ttl=122 time=2.13 ms
64 bytes from 8.8.8.8: icmp_seq=3 ttl=122 time=2.21 ms
64 bytes from 8.8.8.8: icmp_seq=4 ttl=122 time=2.06 ms
^C
--- 8.8.8.8 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3080ms
rtt min/avg/max/mdev = 2.038/2.113/2.217/0.089 ms

Perform a ping from eth0.453

ping -I eth0.453 8.8.8.8

Output

PING 8.8.8.8 (8.8.8.8) from 89.207.131.20 eth0.453: 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=123 time=2.26 ms
64 bytes from 8.8.8.8: icmp_seq=2 ttl=123 time=2.37 ms
64 bytes from 8.8.8.8: icmp_seq=3 ttl=123 time=2.44 ms
^C
--- 8.8.8.8 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2756ms
rtt min/avg/max/mdev = 2.266/2.360/2.444/0.073 ms

Conclusion

Congratulations, you have now configured a server which listens to two VLANs with two gateways. VLAN tagging is not limited to two VLANs, multiple VLANs are supported. You have to add each VLAN according to the network configuration of that VLAN.

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