After digging around on Twitter DB9MAT and me did some experiments with HBlink (see [1]). This is a nice little piece of Phyton code that implements some kind of homebrew protocol that can be used to link some MMDVMHosts together. After cloning the github repository on an Ubuntu 16.04 system I just had to install a Phyton library for bitstream operations. After that the binary hblink.py can be launched. Of course it needs some configuration.
A sample configuration is contained in the github repo and can easly be adapted to your needs. For testing purposes I use the master part of HBlink with this configuration:
[MASTER-1]
MODE: MASTER
ENABLED: True
REPEAT: True
EXPORT_AMBE: False
IP: 169.254.255.256
PORT: 54000
PASSPHRASE: s3cr37w0rd
After adding an incoming firewall rule to allow the incoming 54000/UDP traffic all is ready to go. For testing purposes I changed my config of MMDVMHost to connect to my HBlink instance. The relevant part of the MMDVMHost config is:
[DMR Network]
Enable=1
Address=169.254.255.256
Port=54000
# Local=3350
Password=s3cr37w0rd
RSSI=0
Slot1=1
Slot2=1
Debug=1
Launching MMDVMHost connects to HBlink seamlessly. Running that both time slots and talk groups are routed between all connected MMDVMHost instances. For testing HBlink we had a little DMR session with DB9MAT, DG1TAL, DG9VH, DL5BQ, and DO2BN.