I have been working on your case there are some thing that i would like you to try:
Did you st up the definition of the THR_SERIAL_TUN_ROUTER to 1 in the config.h file ?
#define THR_SERIAL_TUN_ROUTER 1
When you run the Thread_KW_Tun with a factory reset? (using 1 instead of 0)
sudo ./bin/Thread_KW_Tun /dev/ttyACM0 fslthr0 1 25
Are both of the devices (thc and router) on the same channel? (I see that the router could not get connected)
Could you please check your raspberry configuration, we have had some issues like yours but it was caused by their linux lack of permissions or some linux configuration.
I'll leave some screenshots of the result I got using Ubuntu 16.4.03
From the host controlled device:
From the router:
From the ubuntu terminal:
Could you please confirm there is communication between the node and the device? or could you please try the following :
Ping HCD device:
Ping fslthr0 interface
Ping the same IP but forcing the interface:
#ping6 fd01::3ead:7c16:37b5:e6ef:701a -I fslthr0 -c 1
I believe you are following the Kinetis FSCI Host Application Programming Interface document, am I right?
Where did you get the address you are pinging? Could you please give me some more details of how are you doing it?