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Tutorial: IPv6 ping

Simon Duquennoy edited this page Nov 5, 2018 · 14 revisions

We will continue here from our hello-world example (see tutorial:hello-world) with shell enabled (see tutorial:shell). We will look at IPv6 communication (see doc:ipv6). Note that it is possible to ping even a native node: when running it with sufficient permissions (e.g. sudo), native nodes start a tun interface and can be pinged. Here we look at pinging hardware nodes. Compile the project and upload it to both nodes (either by not specifying MOTES at all, which will upload to all, or by listing both tty devices e.g. with MOTES=/dev/ttyUSB0 /dev/ttyUSB1).

Log in to one node (e.g. make TARGET=zoul MOTES=/dev/ttyUSB0 login) and get its link-local IPv6 address via the shell:

> ip-addr
Node IPv6 addresses:
-- fe80::212:4b00:616:fc4

The, log in to the other node, and ping the first node's IPv6 address, e.g.:

> ping fe80::212:4b00:616:fc4
Pinging fe80::212:4b00:616:fc4
Received ping reply from fe80::212:4b00:616:fc4, len 4, ttl 64, delay 31 ms

If you enable IPv6 INFO logs (set #define LOG_CONF_LEVEL_IPV6 LOG_LEVEL_INFO in your project-conf.h), you will see more information. On the source host side:

> ping fe80::212:4b00:616:fc4
Pinging fe80::212:4b00:616:fc4
[INFO: ICMPv6    ] Sending ICMPv6 packet to ff02::1a, type 128, code 0, len 4
[INFO: IPv6      ] packet received from fe80::212:4b00:616:fc4 to fe80::212:4b00:616:fcc
[INFO: IPv6      ] icmp6: input length 48 type: 129 
[INFO: ICMPv6    ] Received Echo Reply from fe80::212:4b00:616:fc4 to fe80::212:4b00:616:fcc
Received ping reply from fe80::212:4b00:616:fc4, len 4, ttl 64, delay 70 ms

And on the destination host side:

> ping fe80::212:4b00:616:fc4
Pinging fe80::212:4b00:616:fc4
[INFO: IPv6      ] icmp6: input length 48 type: 128 
[INFO: ICMPv6    ] Received Echo Request from fe80::212:4b00:616:fcc to fe80::212:4b00:616:fc4
[INFO: ICMPv6    ] Sending Echo Reply to fe80::212:4b00:616:fcc from fe80::212:4b00:616:fc4
[INFO: IPv6      ] Sending packet with length 48 (8)
[INFO: ICMPv6    ] Sending ICMPv6 packet to fe80::212:4b00:616:fcc, type 155, code 0, len 2

You may wonder how the node found out one another's MAC address. By default UIP_ND6_AUTOFILL_NBR_CACHE is enabled (try the make viewconf command, doc:configuration), which lets the node derive the MAC address from the EUI-64 contained in the IPv6 address. Contiki-NG enables this feature by default, but one can also run IPv6 Neighbor Discovery instead by enabling UIP_ND6_SEND_NS.

You can inspect a node's neighbor table at any time with the shell command ip-nbr:

> ip-nbr
Node IPv6 neighbors:
-- fe80::212:4b00:616:fc4 <-> 0012.4b00.0616.0fc4, router 0, state Reachable 
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