VPN troubleshooting guide

VPN has become the essential tool in the last few months but it can be tricky to troubleshoot. Read our guide on common VPN issues and how to fix them.

VPN troubleshooting guide

VPN has become the essential bit of software in the last few months as everyone made the rapid switch to working from home. It's the tool which allows you access into the work network and allows everyone to keep working safely and securely. Unfortunately with the sudden rapid uptake of this we have seen multiple requests for help from businesses outside our managed service who were not quite as prepared as they anticipated and from that we have collated some of the more common issues. Hopefully this guide can help you troubleshoot some of them and get things working better.

Old or wrong VPN software

Software moves fast and gets upgraded often, maybe your company has changed software since you last used the VPN. It's best practice to ensure all staff have the latest version of the software you need to use, VPNs are picky and so even a slight version mismatch can cause a world of trouble.


One of the more common issues we have seen are VPNs that disconnect. This tends to be a result of either an issue at the home or occasionally a very busy company network.

The first thing to check in the home is Wi-Fi signal, if you have a weak or intermittent connection then this can cause the VPN to disconnect (they're quite sensitive at times).

Next make sure someone in the house isn't using all the bandwidth. Is someone streaming Netflix or YouTube? If there isn't much bandwidth to go around then it can make the connection seem very slow or even non-functional so it might need everyone to share a little bit. You can set Netflix and YouTube to stream at lower quality so you could try suggesting that.

Lastly, if the congestion is with the company end then this is going to be a bit trickier to resolve. It might be worth upgrading the VPN endpoint to something a bit more powerful, or increasing the bandwidth to the office if the connection capacity is the issue. You could always give us a call on 03300 882130 to discuss possible network equipment upgrades or faster broadband connectivity.

Mobile data, i.e. 3G and 4G dongles

If you are working remotely and using a mobile dongle such as 3G, 4G, or even 5G modem then this might prevent your VPN working. Mobile networks typically use something called NAT on their mobile data, this means that some types of VPN won't work at all, particularly anything using IPSec.

If you're using mobile broadband and your VPN won't connect then speak to your IT team to see if there is an alternative type of VPN you can use that is more tolerant to NAT. If there isn't then you'll need to find a Wi-Fi hotspot to connect via instead, or use your home broadband if you have it. If you don't have broadband at home then speak to your employer to see if they can pay to have broadband installed.

Firewall Issues

Laptop and desktop firewalls also sometimes cause issues with the functioning of VPN as it keeps check on all the data flowing in and out of your connection. Firewalls are protective of the traffic coming to the machines. However it is key to ensure safety whilst on the internet so for this issue its best to talk to your company IT for assistance or take us up on our offer of 30 mins free consultancy. We want to keep you working but want to keep you safe too!

Restart your VPN or computer

If all else fails turn it off and on again. Start by restarting the VPN as thats the quickest and easiest, but then try restarting the full computer. This fixes a whole host of issues! Arguably we should have put this first in our list.

Last Thoughts
Hopefully this guide give you the basic tools to help you fix some issues however for a full in-depth review of your connectivity for your business please call us. We would be happy to help and the first 30 minute session is on the house!