More than One Flex-6000 on a Network – Configuring your Ports

It took me a while to get my head around this one, as I had been using identical ports with several Flex-6000 radios – but with one big caveat:  In my past usage only one radio per site was powered up at the same time.

It didn’t work when I wanted to leave more than one radio running at my main QTH.

Obviously my configuration was creating conflicts, as basically I’d considered each radio to be interchangeable without properly setting them up to be simultaneous with each other.

Time to do some research and ask for some guidance.

Quick executive summary for those readers who need results right away:

  1. Assign a different pair of external ports for each radio through each radio’s SmartLink setup. The internal port pairs remain UDP 4993 and TCP 4994 for every radio.  

  2. Usually you will want to assign your radios a static internal network IP address, but it is best to do this through a MAC address binding in “Static Lease” (also called “DHCP Reservation”) at your router.

  3. Then create separate Port Forwarding rules for each radio‘s pair of ports in your Router, using your SmartLink configured external and internal pairs with their protocols and your router configured Static Lease IP address.

Internally your radios use UDP 4993 and TCP 4994.  This Port Address pair is the same for each Flex-6000.

But what you use Internally can be translated/mapped to a different External Port Address.

Externally your radio can use whatever port number you configured them for, once it is translated.

FlexRadio Systems Notes on Port Forwarding (courtesy FRS Dan N7HQ)

The translation/mapping is called “Port Forwarding” and basically hooks an external port to an internal port.  Think of the old fashion telephone operator where they physically plugged your call to the recipient’s phone.

A port is configured to communicate with a protocol.  Think modulation or mode if you are thinking radios.

There will need to be a separate TCP port forward for each radio and a separate UDP port forward for each radio. Put two radios on your network you will then need 4 port forward rules.  Remember the externals are ports you pick and configure through SmartLink when you set up each radio.

Two separate rules for each radio.

Hence THREE radios will need SIX rules….


  • Radio #1 Network IP using port pairs TCP external 21000 – 4994 internal and UDP external 22000 – 4993 internal
  • Radio #2 Network IP using port pairs TCP external 21001 – 4994 internal and UDP external 22002 – 4993 internal
  • Radio #3 Network IP using port pairs TCP external 23000 – 4994 internal and UDP external 23001 – 4993 internal
  • and so on…

These 2x00x external port assignments are arbitrary picks to match the graphics from FlexRadio.

You can pick your own system of external ports.  Just keep track of how you assigned them.  Some hams have clever systems where the indexing of Static Lease IP address last digit is part of how they incremented their port pair assignments. As I have a station identifier number for each of my radios, I am using that number as part of my port pairs.

Your should make your external port assignments above port number 1023 (anything lower is reserved) and should stay clear of known registered/popular ports above 1023 if possible.  If you use the range 49152-65536 your assignment should not have a formal conflict.

The trick is to use a unique external port for every rule.

You assign the external ports for each radio through SmartLink setup for that radio.  Remember you need to have a way to key your radio to setup SmartLink.

They would look like this:

Radio #1 Rules:

  • Network IP – external 21000 – 4994 internal – Protocol TCP
  • Network IP – external 22000 – 4993 internal – Protocol UDP

Radio #2 Rules:

  • Network IP – external 22001 – 4994 internal – Protocol TCP
  • Network IP – external 22002 – 4993 internal – Protocol UDP

Radio #3 Rules:

  • Network IP – external 23000 – 4994 internal – Protocol TCP
  • Network IP – external 23001 – 4993 internal – Protocol UDP

The “Static Lease” is a way to reserve your network’s specific IP address to a particular radio by that radio’s Mac Address.  Remember in most default cases a router assigned your internal network addresses, and for the most part assigns them following rules that unless a Static Lease is set up could issue a different internal network IP address to your radio each time it is started.

A changed internal IP address plays havoc to your port forwarding, as that port forwarding opens per rule specifically configured port numbers by configured protocol for specific internal network addresses.  So if your internal DHCP section of your router assigns different internal IP addresses to a radio, the port following will not follow it.

While you can set a Static IP in the radio through >network >settings, everyone at the FRS Community strongly recommends against it, as there is a better more robust way.  Will take you a minute longer upfront and save lots of time later, especially if you end up troubleshooting down the road.

By setting a DHCP reservation based on the rig’s MAC address – what I’ve called a “Static Lease”, you accomplish the same thing as setting it from the radio end while making the assignment reproducible and constant value within your network.

With a “Static Lease” in the router, the radio will be assigned the same IP address each time it is booted up. Without a “Static Lease”, the router could assign the “radio” IP to other local network objects and break the the port forwarding rules.  Without a “Static Lease” set in your router, your assigning a fixed address in the radio does not prevent the router from assigning the radio IP address to another if the radio is not already on & running.

Setting any device in a DHCP-enabled network to a fixed value will create troubles when DHCP assigns the same IP address value you assigned at the radio end to another device. Remember your router follows only its programmed rules and won’t know about a device end claim to an IP address) to another device. It usually isn’t fun.

Protip: You can get each radio’s MAC address by >Radio Setup > Network while running SmartLink to hand copy or take a screen shot of the radio information.  The Mac address is in the right format there.

Or you can right click while hovering over a radio in SmartLink’s Radio Chooser to copy that radio’s information to clipboard, though it will be formatted differently and labeled “Radio ID.”

One of mine came out as (some of the numbers have been replaced with “x”):

Serial: 5017-7826-6601-xxxx, Max Licensed Version: v3, Radio ID: 00-1C-xD-0x-00-xC, Radio IP: 1xx.0.7.1xx, Radio Internet: Available, Radio Firmware: v3.1.12.51

The Mac address is the “Radio ID” part underlined and in bold, and usually is entered into your router with dashes replaced with colons, like:  00:1C:xD:0x:00:xC

Consider putting a sticky label on the back of your radios with their Mac Address as an aid down the road, and put those Mac addresses in your station documentation.

With a Static Lease assignment the router will recognize a radio’s Mac address and issue it the reserved internal network IP address.

[Easy Explaining:

Mac addresses are kind of like an individual ID number for a specific device connected to the network.  They are supposed to be unique. Kind think of the Mac address like a driver’s license number.

IP addresses come in two main categories – external IP addresses are what the WAN/Internet uses to find your network and internal IP addresses are what the LAN/Your Network uses to “route” traffic to a specific device.   External IP addressing is what identifies your particular network to the rest of the internet.  Internal IP addresses are what your network uses in-house to direct traffic.

Ports are kind of easily thought of as analogous to a frequency and the protocol is kind of like the mode, sort of like using port 4993 UDP is like a frequency setting (gets you communicating on the same space) and the UDP part is agreeing say USB phone (the protocol both ends are using).]

You can alter your assignments and rules to suit your particular setup, following a few cardinal guidelines:

  • Don’t use a well known port, especially one that you might need other access to.
  • Don’t reuse an external port for another radio on the same network.
  • Set up SmartLink for your radio and you Router rules THE SAME by radio.
  • Use the “Static Lease” settings in your router to reserve an internal network IP address by Mac Address for each radio.
  • • Write up a plan for lease reservations and port assignments and save it in your station documentation.

Remember that when you are not on the same network as your radio, SmartLink is your conduit between your GUI (Graphic User Interface) and the radio.

When you are on the same logical network as your radio, you do not need to (nor should you) use SmartLink.

You need to be physically present at the transceiver (or have a remote method to short the key input) to authorize your radio to use SmartLink.

The TCP/UDP port forwarding rules need to be active and also need to be entered during registration (see above).

I asked FRS for some help on exactly how SmartLink works and they shared this graphic:

How SmartLink works (courtesy FRS Dan N7QH)

When we add more radios on the inside of our network firewall things get interesting.

Some references:

The FlexRadio Community thread where several folk helped me out:

FlexRadio’s Whitesheet on (single radio) Port Forwarding:

Mac Address vs IP Address differences explained:

Port Forwarding General Tutorial:

A list of Ports is kept at:

A WikiHow piece on setting up port forwarding:

The same in deeper detail including information of specific routers:

A Protip:  You can look at what ports you are using – from a Windows command prompt “netstat -ano” will start you down the ports rabbit hole.

In my case I am setting up each Flex-6000 in SmartLink to a unique port forwarding pair, and setting up a Static Lease for each radio at each antenna location to let me swap radios easily.

As I have three physical stations and I would like to make my radios interchangeable between sites, I will be setting up and documenting extra Static Leases and Port Forwarding rules based around each radio’s Mac address.  That way I can move radios between sites without worries.  What has to stay consistent is use of a particular external port pair against each networks Static Reservation by Mac address that matches a particular radio.

I’m also recreating a new reference document with all the information, and will put an information sticker on each radio.

Harder to think about, doubly hard to explain, and yet easy in practice.



Special thanks to the following article reviewers:  

    • * Winston KC9FVR – my son, a recent computer science graduate who helped troubleshoot my network, and reviewed my draft
    • * Al K0VW – Alpha Team member who volunteered to review my draft
    • * Dan N7HQ – FlexRadio Systems who reviewed the technical details to help me from giving out incorrect information
    • Howard KY6LA – Alpha Team member who volunteered to review my draft
    • Mike W5JR – Alpha Team member who volunteered to review my draft
    • Tim W4TME – FlexRadio Systems who reviewed the technical details to help me from giving out incorrect information
    • Ria N2RJ – Alpha Team member who volunteered to review my draft
    • and FlexRadio Systems via Dan N7HQ for the graphics and permission to use them.

While these kind folk did courtesy reviews, any mistakes are mine alone

Readers are invited to provide comments or email me (I’m good at QRZ, as they say) with suggestions, corrections or ideas.




2 thoughts on “More than One Flex-6000 on a Network – Configuring your Ports

  1. Salvador D says:

    Thanks Steve for putting this together! 73 EA4GLI

  2. k9zw says:

    Thanking everyone for their kind comments, both here and at the FlexRadio System Community.

    Watch down the road for a bit more write up on Port Forwarding in relationship to other typical remote-enhanced Flex based shack equipment.

    I’m tracking suggestions and will make a bulk edit to the main article later.

    One item pointed out is that some routers merge the static lease idea and port forwarding to basically create port forwarding rules by Mac addresses. It doesn’t seem like a true DHCP reservation is configurable on these routers, but if the port forwarding rules are that well bound to each radio it looks workable.



Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: