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VPN Server: TUN vs TAP

Discussion in 'Asuswrt-Merlin' started by IHazAQuestion, Dec 29, 2012.

  1. IHazAQuestion

    IHazAQuestion Occasional Visitor

    Oct 28, 2012
    Hi all,

    I'm trying to understand the practical differences of connecting to my home VPN server via Merlin's Firmware. I've read up on some of the differences between TUN and TAP, but most of them are super technical and I'm moreso looking for a straight forward answer on practical usage in layman's terms.

    1) I have successfully connected to my home VPN server using TUN. However I was not able (or rather didn't know how) to access any of my home resources (Desktops, RT-N66U admin page, etc).

    2) I understand that if I connect VIA TAP, my remote computer will appear as local and I will be able to see all my devices under "Network Neighborhood" and is very simple. My understanding is that the drawback is that connecting via TAP consumes significant network resources and is "noisy" (for lack of better term).

    I don't necessarily need to be able to access my resources via Network Neighborhood, but I would at least like to RDP into my home desktop from where ever I am, or at the least access shared directories. I don't need much more (right now at least). Can either of these be done via TUN or is TAP the only option?

    Thanks in advance!
  2. RMerlin

    RMerlin Part of the Furniture

    Apr 14, 2012
    TUN is fine for your needs. TAP is only needed for very particular scenarios.

    Make sure you run the OpenVPN client as Administrator, otherwise it will be unable to apply the routes being pushed to it by the OpenVPN server. That's most likely the reason why you can't route to your LAN devices. Either that, or your home LAN uses the same IP range as the network from where you are connecting, which will make it impossible for your client to tell if you are trying to access a local or a remote device when you enter an IP.
  3. mrgenie

    mrgenie Occasional Visitor

    Nov 22, 2012
    For people with low needs TUN will suit every single home network need. If configured properly. There are many reasons that can "block" traffic, but the main points are written by Merlin.

    The benefit of TAP is that every single network service will run (normal home users don't need this I think) over TAP you can also have a class B network running (65k computers/clients) the problem is indeed that if a class B network is setup by people who have no idea what they're doing, you'll most likely need a 1Gbit connection to handle the useless traffic over your network if you have so many clients.
    For security reasons it shouldn't matter whether you take TUN/TAP
    if configured properly however, a TAP network actually has less "noise" then a TUN network, although technically the term "noise" isn't correct.

    Since you have these questions, I take an honest guess you have not much experience with networking, and I strongly advise you to listen to Merlin and stay with the TUN solution.

    But TUN and TAP will serve you perfectly, if configured correctly.
    When I started with openVPN a lot of questions I had myself, and actually this forum or Merlin is the wrong source. For specific questions, simply go to the openVPN forums. There are gurus there that can help you out if something doesn't work.

    I haven't have much experience with Tunnel networking myself. I run a network crossing the continent with a few thousand clients, so TUN is no option for me. But setting up a properly configured TAP will take some time, especially for a first time person who wants to learn how to do it. Unless you really need it, TUN will suit every windows/linux/osx home network service, including RDP (VPN can be faster in some cases, not always!) file sharing, etc..

    If you have more questions, people here, myself included might try to answer them, but I really advise you to ask in the openVPN forums. There you find the openVPN gurus! And they know some tricks you won't even be able to find by using google ;)
  4. octopus

    octopus Very Senior Member

    Jul 17, 2012
    What is the difference between a TUN device and a TAP device?

    A TAP device is a virtual ethernet adapter, while a TUN device is a virtual point-to-point IP link.
    Level 2 and level 3 networks.
  5. aminutestime

    aminutestime New Around Here

    Apr 8, 2015
    I had the same question years ago and attempted to answer it in straightforward terms (which personally I found lacking in other resources) on my blog:
    An OpenVPN Primer

    Hope it helps someone
    mattiL, CyberMew and martinr like this.

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