Add description for radvd on wlan0 and Windows client

[Josar]

As i did in my PR i added additional information to the readme, but i can not acces teh wiki, or can i?

I would like to add additional information in the 6lbr page.
The radvd github download link could point to the original repo.

Additional Setup radvd to advertise route for wlan devices.
This seems not neccessary for the rpi´s but my windows host always tries to use the standart gateway.
So the ping packets will be send to the router.

sudo nano /etc/radvd.conf

interface wlan0
{
    AdvSendAdvert on;
    AdvSourceLLAddress on;

    prefix fd18:a:b:1::/64
    {
        AdvOnLink off;
        AdvAutonomous on;
        AdvRouterAddr on;
    };

    abro fd18:a:b:1::1
    {
        AdvVersionLow 10;
        AdvVersionHigh 2;
        AdvValidLifeTime 2;
    };
};

Set up border router lowpan and wlan addresses

sudo ifconfig lowpan0 add fd18:a:b:2::1/64
sudo ifconfig wlan0 add fd18:a:b:1::1/64

sudo sysctl -w net.ipv6.conf.all.forwarding=1
sudo ip route add fd18:a:b:2::/64 dev wlan0

Set up network device 1 RPI

sudo ifconfig wlan0 add fd18:a:b:1::2/64

Set up network device 2 Windows
some good to know commands

netsh interface ipv6 show /?
netsh interface ipv6 show addresses
route print

Find adapter name with ipconfig and replace it for WiFi if an other connection is used.

netsh interface ipv6 add address WiFi fd18:a:b:1::3/64 

Adding a route should not be neccessary as a automatically assigned address should be in the routing list as the RPI does route advertisement.

Ping and force the usage of the new address to prevent the system to ping with a address with higher priority

ping -6 -S fd18:a:b:1::3 fd18:a:b:1::1

This will ping with the automatically assigned address

ping -6 fd18:a:b:1::1

If Wireshark shows "Echo (ping) request" from lowpan but no reply from windows.
Wifi connection has to be set to privat as the "File and Printer Sharing" is not able in public network.
Maybe also Windows firewall rule "File and Printer Sharing (Echo Request)" for inbound rules has to be deactivated

If wireshark shows "Echo (ping) reply" from windows but rpi does not accept them.
Then the reply does not addrressed to rpi as destination, this happens when no route is advertised.

Frame 258992: 66 bytes on wire (528 bits), 66 bytes captured (528 bits) on interface 0
Ethernet II, Src: IntelCor_03:7b:f9 (ac:fd:ce:03:7b:f9), Dst: Raspberr_41:92:d6 (b8:27:eb:41:92:d6)
    Destination: **Raspberr_41:92:d6 (b8:27:eb:41:92:d6)**
    Source: IntelCor_03:7b:f9 (ac:fd:ce:03:7b:f9)
    Type: IPv6 (0x86dd)
Internet Protocol Version 6, Src: fd18:a:b:1::3, Dst: fd18:a:b:2:dedc:20b7:3c21:8b3e
Internet Control Message Protocol v6

force traffic to rpi wlan net to use wifi and the configured local ip.

netsh interface ipv6 add route fd18:a:b:1::/64 WiFi fd18:a:b:1::3 metric=10