Setup a RIOT OS 6LowPAN border router

5 Apr

After playing around with the gnrc_networking example in the last post the next step is to setup a border router. Border routers are the communication pieces in between a 6LowPAN network and normal LAN/WAN. Because normal computers/hardware don’t bring IEEE 802.15.4 capable radios with them you need to change one development board into a slip radio. The host system communicates over serial with the slip (serial line ip) radio and therefore is able to send and receive messages to the IEEE 802.15.4 network.

Prerequisites:

The needed prerequisites can of course vary based on your goals. A minimal setup would be in this case:

  • ARM GNU GCC Toolchain
  • UART/COM Port

Building the border router image

The slip radio / border router image is also located in the `examples` directory of the RIOT folder. It is called `gnrc_border_router` and can be built with:

git clone https://github.com/RIOT-OS/RIOT.git
cd RIOT/examples/gnrc_border_router
make BOARD=cc2538dk
...
   text	   data	    bss	    dec	    hex	filename
  72652	    144	  24168	  96964	  17ac4	RIOT/examples/gnrc_border_router/bin/cc2538dk/gnrc_border_router.elf

The .elf/.bin files are again put inside the `bin/cc2538dk` folder – now flash the firmware to the board.

Setting up bridging interface

RIOT already comes with a very handy script that does the whole bridging work for you. Further explanation can be found in their wiki.

To get it working you first need to compile additional tools bundled with RIOT:

cd RIOT/dist/tools/ethos
make clean all
cd RIOT/dist/tools/uhcpd
make clean all
cd RIOT/dist/tools/ethos
sudo sh start_network.sh /dev/ttyUSB0 tap0 2001:db8::/64

The last line starts the shell script and hands in the device address of the UART port (/dev/ttyUSB0), the desired bridge interface name (tap0) and the IPv6 prefix for the network. You may need to change the UART device in your setup!

Flash the `gnrc_networking` example (as explained here) to a second device and start it up. You should get something like the following output on the host:

net.ipv6.conf.tap0.forwarding = 1
net.ipv6.conf.tap0.accept_ra = 0
----> ethos: sending hello.
----> ethos: activating serial pass through.
----> ethos: hello reply received
----> ethos: hello reply received
uhcp_client(): sending REQ...
got packet from fe80::3c6e:2aff:fe8d:a253 port 37622
uhcp: push from fe80::3c6e:2aff:fe8d:a253:37622 prefix=2001:db8::/64
gnrc_uhcpc: uhcp_handle_prefix(): got same prefix again

and should now see on the second board that it got the prefix’ed address:

> ifconfig
Iface  7   HWaddr: 9c:00  Channel: 26  Page: 0  NID: 0x23
           Long HWaddr: 00:12:4b:00:06:15:a8:6b
           TX-Power: 0dBm  State: IDLE
           AUTOACK  MTU:1280  HL:64  6LO  RTR  RTR_ADV  IPHC
           Source address length: 8
           Link type: wireless
           inet6 addr: ff02::1/128  scope: local [multicast]
           inet6 addr: fe80::212:4b00:615:a86b/64  scope: local
           inet6 addr: ff02::1:ff15:a86b/128  scope: local [multicast]
           inet6 addr: ff02::1a/128  scope: local [multicast]
           inet6 addr: 2001:db8::212:4b00:615:a86b/64  scope: global
           inet6 addr: ff02::2/128  scope: local [multicast]

           Statistics for Layer 2
            RX packets 21  bytes 1762
            TX packets 20 (Multicast: 3)  bytes 1755
            TX succeeded 0 errors 0
           Statistics for IPv6
            RX packets 16  bytes 1560
            TX packets 20 (Multicast: 3)  bytes 1786
            TX succeeded 20 errors 0

Now you can try pinging your device from the linux host system:

ping6 2001:db8::212:4b00:615:a86b
PING 2001:db8::212:4b00:615:a86b(2001:db8::212:4b00:615:a86b) 56 data bytes
64 bytes from 2001:db8::212:4b00:615:a86b: icmp_seq=1 ttl=63 time=55.4 ms
64 bytes from 2001:db8::212:4b00:615:a86b: icmp_seq=2 ttl=63 time=46.1 ms
64 bytes from 2001:db8::212:4b00:615:a86b: icmp_seq=3 ttl=63 time=58.8 ms
64 bytes from 2001:db8::212:4b00:615:a86b: icmp_seq=4 ttl=63 time=52.7 ms
64 bytes from 2001:db8::212:4b00:615:a86b: icmp_seq=5 ttl=63 time=43.0 ms
^C
--- 2001:db8::212:4b00:615:a86b ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4007ms
rtt min/avg/max/mdev = 43.096/51.233/58.813/5.829 ms

Et voila you can now access the 6LowPAN network with RIOT devices from your linux host – and the other way around. If you want to enable your devices to reach the internet you will need to add additional routes to the host system (for correct routing).

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