How does VPN overcome port block?

Question

Background:

A few days back I wanted to play AOE2 over internet. For that I used Voobly application for finding the users and launching the game. But problem was that since my local ISP had blocked port 16000, I was unable to play. I asked the local ISP to forward the port 16000 and they didn't know what did that mean.

After that I installed Hideme VPN application and it somehow did the port forwarding and I was able to play.

Question:

How does the VPN overcome the port blocking restriction? Isn't all the traffic still go through my router, so then how did that happen?

Note: I first asked this at Network Engineering , they told me to move it here.

Solution 1

Without VPN your traffic is going to the router and it forwards it to the ISP. Let's say that the traffic is "naked", so the ISP can inspect the traffic and when they find your packets aimed to port 16000 they block them.

With a VPN the traffic going out of your computer is encrypted and then put inside "innocent" packets that act as a wrapper using a port like 8080 or 8081. Your ISP can still inspect your traffic but they will find port 8080 and as it is not the usual suspect they let them pass.

When your traffic gets to Hideme servers they decrypt and then forward the traffic to the final destination.

Solution 2

VPN isn't necessarily overcoming port blocking as the vpn still needs a port to use which most vpn's that use L2TP tunnenling use ports 500 and 4500. It depends which type of tunneling the application uses, as well as ports for vpn applications can be modified.

Essentially, a VPN is tunnel network to another system to allow you secure connections for various things. From hiding your true IP from websites, to overcoming port blocking for applications, because the tunnel uses a port thats not blocked and the application essentially uses the system's network you connected to for communication through the tunnel.

Since you called your ISP about it, most tech support representatives, the ones that answer your call first, generally don't need/require the need to know much about networking. So, if you do ever call them again for opening a port for you etc, just ask for their network egineer or IT Department lol. They usually will know what you are talking about and can give you a more informative answer on whether they can do that for you or if they can't.

Comments

[InQusitive]

So, is it a disadvantage to the ISP who blocked that port for some purpose? Or it doesn't matter to them?(when we use VPN)

[Frostalf]

@InQusitive It doesn't matter to them, but it does cost them in resources to block ports as it causes overhead on their network switches. Most times they have a good reason from their end to block certain ports. Ranging from ports most commonly abused to ports their clients abuse. etc.