Learn how to troubleshoot and fix VLAN connectivity issues on Linode, a cloud computing platform that allows you to create private networks for your servers.
Sometimes you may encounter VLAN connectivity issues, such as not being able to ping or access your Linodes on the same VLAN, or not being able to reach external resources from your VLAN. In this article, we will show you how to troubleshoot and fix some common VLAN connectivity issues on Linode, using a real-life example from a user who posted their problem on the Ask Ubuntu forum.
Table of Contents
Problem Description
The user had two Linodes in the same data center, both attached to the same VLAN. They were able to ping each other using their private IP addresses, but they were not able to ping or access any external resources, such as Google or other Linodes outside the VLAN. They also noticed that their Linodes had different default gateways, which seemed to be the cause of the problem.
Solution Explanation
The solution to this problem was to change the default gateway of the Linodes to match the VLAN gateway, which is the first IP address in the VLAN subnet. For example, if the VLAN subnet is 192.168.128.0/24, then the VLAN gateway is 192.168.128.1. This way, the Linodes can route their traffic to the VLAN gateway, which will then forward it to the appropriate destination.
Step 1: To change the default gateway of a Linode, you need to edit the network configuration file of the operating system. The exact location and format of this file may vary depending on the OS and the network manager you are using, but in general, you need to find the line that specifies the gateway and replace it with the VLAN gateway. For example, on Ubuntu 20.04 with Netplan, the network configuration file is located at /etc/netplan/01-netcfg.yaml, and it may look something like this:
network:
version: 2
renderer: networkd
ethernets:
eth0:
dhcp4: no
addresses:
- 192.168.128.10/24
gateway4: 45.79.0.1
nameservers:
addresses:
- 66.228.42.5
- 96.126.106.5
In this case, you need to change the gateway4 value from 45.79.0.1 to 192.168.128.1, which is the VLAN gateway. The file should look like this after the change:
network:
version: 2
renderer: networkd
ethernets:
eth0:
dhcp4: no
addresses:
- 192.168.128.10/24
gateway4: 192.168.128.1
nameservers:
addresses:
- 66.228.42.5
- 96.126.106.5
Step 2: After saving the file, you need to apply the changes by running the following command:
sudo netplan apply
Step 3: You can verify that the default gateway has been changed by running the following command:
ip route show
You should see something like this:
default via 192.168.128.1 dev eth0 proto static
192.168.128.0/24 dev eth0 proto kernel scope link src 192.168.128.10
The first line shows that the default gateway is now 192.168.128.1, which is the VLAN gateway. The second line shows that the Linode is part of the VLAN subnet 192.168.128.0/24.
You need to repeat this process for the other Linode on the same VLAN, using its own private IP address. After that, you should be able to ping and access external resources from both Linodes, as well as communicate with each other on the VLAN.
Frequently Asked Questions (FAQs)
Question: What is a VLAN?
Answer: A VLAN is a virtual local area network that allows you to create private networks for your Linodes, isolating them from other traffic on the internet and within the same data center. VLANs can enhance the security and performance of your applications, as well as simplify the network configuration.
Question: How do I create a VLAN on Linode?
Answer: You can create a VLAN on Linode by following the steps in this guide. You need to have at least two Linodes in the same data center, and you need to enable the VLAN feature on your account. You can then create a VLAN and attach your Linodes to it, assigning them private IP addresses from the VLAN subnet.
Question: How do I troubleshoot VLAN connectivity issues on Linode?
Answer: If you encounter VLAN connectivity issues on Linode, such as not being able to ping or access your Linodes on the same VLAN, or not being able to reach external resources from your VLAN, you can try the following steps:
- Check the network configuration of your Linodes, and make sure that they have the correct private IP addresses and default gateways for the VLAN.
- Check the firewall rules of your Linodes, and make sure that they allow traffic from and to the VLAN subnet and the VLAN gateway.
- Check the status of the VLAN interface on your Linodes, and make sure that it is up and running.
- Check the status of the VLAN on the Linode Cloud Manager, and make sure that it is active and has the correct subnet and gateway.
- Contact Linode support if none of the above steps resolve the issue.
Summary
In this article, we showed you how to troubleshoot and fix VLAN connectivity issues on Linode, using a real-life example from a user who posted their problem on the Ask Ubuntu forum. We explained how to change the default gateway of the Linodes to match the VLAN gateway, which is the first IP address in the VLAN subnet. We also provided some FAQs and a summary of the main points.
Disclaimer: This article is for informational purposes only and does not constitute professional advice. Always consult with a qualified IT expert before making any changes to your network configuration.