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SmartLink vs. VPN radio connection - the differences of each

Mike-VA3MW Administrator, FlexRadio Employee, Community Manager, Super Elmer, Moderator admin

I want to share the difference between a SmartLink connection or a direct VPN connection for a remote operation. I put this together as a reference for anyone considering adding a VPN to their remote setup.


  • It is built into SmartSDR and is free with your radio purchase
  • FlexRadio's SmartLink servers are required to broker the initial peer to peer connection
  • It is simple to configure
  • It is a secured network communication path
  • It is easy to share your radio as a resource
  • It is a peer to peer connection - meaning no intermediate server is required other than the initial login via the SmartLink server
  • It requires 2 ports being forwarded on your router, usually handled by uPNP (Universal plug and play)
  • Manual port forwarding is available
  • The audio being sent over the internet is compressed requiring less bandwidth
  • It is supported by FlexRadio technical support
  • Some external programs work with SmartLink such as FRStack
  • It is built into SmartSDR, Maestro, SmartSDR for MAC, SmartSDR for iOS and DogPark SDR
  • no networking experience is required

VPN Solution

  • The VPN must support layer 2 bridged network communications such as SoftEther (many VPNs do not)
  • The VPN connected devices must be on the same subnet as the radio - this can be an advanced configuration issue for some VPN solutions
  • There is no requirement to have access to the SmartLink servers and is a stand-alone solution
  • The audio is not compressed as it is on SmartLink resulting in more bandwidth usage
  • A VPN solution is not supported by FlexRadio technical support meaning you are 'rolling your own'
  • VPN configuration can be a complex solution for those that have limited networking education
  • SmartSDR clients operate as a local Lan connection

FlexRadio does realize there is a request that SmartSDR supports a direct IP addressing option as well which SmartSDR for MAC and iOS currently provide. This has been logged as a feature request.


  • Jon_EA2W
    Jon_EA2W Member ✭✭

    Hi Mike,

    Thank you for the comparison about SmartLink and VPN. For outside US users, it might happen that a VPN has much less latency than Smartlink for obvious reasons.

    I personally chose to use a VPN because the difference in latency between both here in Europe is important, around 10-15ms for the VPN and around 100-150ms for Smartlink.

    It would be very good if Flex could consider to have a Smartlink server in Europe considering the amount of users there are in Europe and Asia.

    My 2 cents.

    73! Jon

  • W9WLX_Chuck
    W9WLX_Chuck Member ✭✭

    Jon, my understanding is once the authentication occurs, the connection path is direct client to server--no routing through the Smartlink server takes place.


  • Mike-VA3MW
    Mike-VA3MW Administrator, FlexRadio Employee, Community Manager, Super Elmer, Moderator admin

    Hi Jon

    There really is no requirement for a dedicated server in the EU since it will not be any faster. All the SmartLink server does is provide the WAN IP address and the 2 ports your radio is using. Radio traffic does not travel through SmartLink servers. It is just a simple 'look up' service. This is a common misunderstanding. The user client is a direct IP connection to the radio and this is what is called a peer to peer connection.

    There is a large difference in the amount of data moved on the VPN when compared to a SmartLink connection.

    I have used both SmartLink and a Softether VPN connection and I have not measured an operational difference on 3.2.39.


  • Jon_EA2W
    Jon_EA2W Member ✭✭
    edited September 2021

    Hi Chuck and Mike,

    Thank you for your feedback. I didn´t know smartlink was a peer to peer connection too! My guess was it was not because of the difference in latency between one solution and the other.

    Sold my 6400 but my new 6600 is on the way, I hope I can make additional tests next weekend and recheck latencies. Should be very similar based on what you said. Will report back in case I see a big difference.

    73! Jon

  • Pena
    Pena Member
    Hi Jon, Chuck and Mike

    In my case I'm using Flex6400 remotely over 4G LTE connection on my laptop. The problem is, that my ISP is using CGNAT (remote site), so only working solution is Softether. Softether is running on remote PC, which I'am using for FT-8 over RDP connection.

    Problem is with my iPhone, since it is using L2TP and it's blocked by CGNAT. I have Teltonika RUTX11 on it's way, and it supports also Zerotier, so let's see how that solution works. Zerotier has a client for IOS, so it might work :)

    OH6PP Pena
  • K5SRT_Ross
    K5SRT_Ross Member ✭✭

    Whose VPN do you know supports this? Thinking it might be a good backup.

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