Thread border router - IPV6 DHCPv6 problem

[Carry Irving]

Hi there,

I'm using ASUS RT-AC1900P router with IPv6 DHCPv6 on. RPi gest its own IP with prefix specified in router but interface wpan0 (wpantund) not. I have configured the Router properly, the static IPv6 with /62 prefix. My RPI seems to get the prefix successfully, But my Thread nodes don't have an IPv6 address created using /62 prefix. My border router works on v0.11.0-1.alpha firmware. How can I solve this problem in this case?

eth0      Link encap:Ethernet  HWaddr B8:27:EB:F7:52:E6  
          inet addr:192.168.2.204  Bcast:192.168.2.255  Mask:255.255.255.0
          inet6 addr: 2001:250:4000:1230::1bec/128 Scope:Global
          inet6 addr: fdb3:867c:4acf::1/64 Scope:Global
          inet6 addr: fe80::ba27:ebff:fef7:52e6/64 Scope:Link
wpan0     Link encap:UNSPEC  HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  
          inet6 addr: fdff:cafe:cafe:cafe:38b0:d362:515:aa91/64 Scope:Global
          inet6 addr: fe80::38b0:d362:515:aa91/64 Scope:Link
          inet6 addr: fdde:ad00:beef::98e0:3f4c:428b:abc4/64 Scope:Global

> ipaddr
fdde:ad00:beef:0:0:ff:fe00:c000 
fdff:cafe:cafe:cafe:df20:60c:6f0a:de9c 
fdde:ad00:beef:0:8625:f5f0:b3df:6f10
fe80:0:0:0:d4ed:2599:a745:c938
Done

Thanks. xiangcai

[Jørgen Holmefjord]

Hi,

From your ifconfig output, it is clear that your border router have not been assigned a /62 or lower prefix address for eth0:

inet6 addr: 2001:250:4000:1230::1bec /128 Scope:Global

Are you running stock firmware on your ASUS router? I see you have seen my comment in this thread. As I said, on many routers DHCPv6 does not work correctly and they are only providing /6 4 prefix or higher addresses. You should try OpenWRT on your router (if supported), or try with a router that correctly assigns IPv6 addresses with /62 or lower prefix.

Best regards,

Jørgen

[Carry Irving]

Hi,

Does it work if I assign a specific static ipv6 address with prefix length to that interface? Such as modify the file `/etc/config/network` like the following shows:

config interface 'wan6'
        option ifname 'eth0'
        option _orig_ifname 'eth0'
        option _orig_bridge 'false'
        option proto 'static'
        option ip6addr '2001:1234:4567::2/48'
        option ip6assign '62'

root@OpenWrt:~# ifconfig
eth0      Link encap:Ethernet  HWaddr xxxx
          inet6 addr: 2001:1234:4567::2/48 Scope:Global

I had tried it, but Thread Nodes didn't have an IPv6 address created using /62 prefix. Why?

Thanks~

[Jørgen Holmefjord]

It was a bit unclear from your last comment if you set the static address on the router or on the boarder router? Could you provide the log generated by the command "ip -6 route" on the border router? It should help us determine if you have the proper prefix in the routing table. What prefix do you get from your ISP? Did you flash your router with a custom firmware (OpenWRT, etc.)?

[Carry Irving]

I'm sorry for that. I used the pre-built Nordic BR v0.11.0 which distconnected with upstream router.  I just tried it and want to know how do the Thread Nodes get the specific prefix from BR. How the BR works with Thread network?  There is no relevant information in the official documentation.

By the way, can I flash my router with OpenWRT(LEDE) on Raspberry pi 3B. Does it work? I want to try it next.

Appreciate for your reply.

[Jørgen Holmefjord]

The border router use wpantund to talk to the Thread NCP. There are scripts running on the BR that willcheck IPs in eth0 interface, and if there is any with prefix less than /63 (e.g. /62 or /48) it should create a subnet out of it. If you need it, I can check with our Thread developers if we have some more documentation on this. 

I have not tested OpenWRT/LEDE on RPi3, but it looks like it should be possible.

[Carry Irving]

Yeah, I really need more documentation about that.

And I had tried the OpenWRT/LEDE on RPI3 recently, it worked fine.

Thank you~

[Jørgen Holmefjord]

The BR will run this startup script. The IPv6 prefix is assigned by the function assign_global_ipv6_addrs().In the first step we search for appropriate global prefix in the routing table ("ip -6 route" piped to sed). If we find one, we create a proper /64 prefix out of it and pass this to wpantund (wpanctl config-gateway $prefix -d). Note that "wpanctl config-gateway $prefix -d" can be used to pass any external prefix, which could be useful in some early stage development. 

If you take a look at these scripts, you should be able to figure out how this is done.