It took over a week, a complete network reconfiguration, and a lot of google searching to figure this one out.

I wanted my MMDVM on P25 for a number of reasons.

It should have been as easy as turning the mode on, and selecting a default host, right? well… maybe?

It didn’t work that way for me – I went through a TON of settings and attempts to get P25 net to connect. The gateway settings seemed to have no effect. I had 42010 (the outgoing P25 port) open on my router and wireless router – even though I was using uPnP, I set up port forwarding… nothing.

I was about to give up, and then…. I found the answer:

The Pi-star internal firewall needs to be set in a specific manner for P25. In this case, I modified their directions slightly, and I’m reposting my work here:

Log into pi-star, and enter into your configuration tab, then select the SSH window. Then log into the pi with your username and password

(enter superuser mode)


(change your current directory to root)

cd /root

give read-write access to the root folder


create the firewall rules file and edit it in nano

nano ipv4.fw

next, enter these two lines EXACTLY in the terminal window, hitting enter after each line.

note: I changed the port numbers from their recommendation to encompass the P25 port

iptables -A -OUTPUT -p udp --dport 41001:41999 -j ACCEPT

iptables -t mangle -A POSTROUTING -p udp --dport 41001:41999 -j DSCP --set-dscp 46

then hit ctrl+o to save the file, and hit enter when it prompts you. ctrl-x will then exit.

IF it gives you a red bar across the bottom when you hit ctrl-o, then for some reason read-write access didn’t take. exit (without saving), try the rpi-rw command again, then go through the nano steps above again.

As soon as i did this, I suddenly got a connection to p25 net, and the system began to work flawlessly – now i need to reprogram my radio, and reconfigure my portable hotspot.

One thought on “MMDVM on P25…”
  1. One note: If, after the above instructions, you get a situation where the P25 Net light starts green, then turns to red, verify that any P25 reflectors selected in the MMDVM software are active. If a reflector goes offline, but you are still pointing your hotspot to it, it will have the green-then-red response. Selecting “None” is also an option, from what I’ve been told, and will allow the system to function properly.

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