[gentoo-server] ipv6 + dhcpv6 + unique local addresses

[Halassy Zoltán]

Hello!

Is there anyone who has experience with unique local addresses (fc00::/7)?

I have experience with radvd and isc dhcp (in ipv6 mode too with the -6 
flag), I could already configure stateful configuration with global 
unicast (2000::/3) addresses with working default gateway.

What I am trying to do now is to create a local IPv6 network space with 
a dhcpv6 server (amd64 gentoo), which is only reachable via VPN. The 
network does not have any router, it's isolated. IPv4 is not an option, 
and DHCPv6 is mandatory. The clients are mostly Windows Vista+ systems. 
What I am seeking is the proper way to do this. I could make it work, 
but I consider this a hack.

I generated a random IPv6 address range, but I will use the 
fd00:2001:db8::/64 prefix in the description.

Problem #1:

DHCPv6 works fine, it pushes an IPv6 address to the client, but the 
client does not get the prefix information with it. Eg.: client gets 
fd00:2001:db8::ffff:fffe/128 as address, but missing the local route 
information for fd00:2001:db8::/64 through the interface.

Problem #2:

If I use radvd advertising the fd00:2001:db8::/64 prefix, the client 
configures that up, but it also configures a bogus default route too, 
which is definitely unwanted.

Hack #1:

Using dhcp and radvd together actually works (even though it's very 
ugly). It does not ruin an existing IPv6 connection, and does not cause 
problems when originally there is none. I just fear it *might*.

Hack #2:

It is possible to create static (even on-link) routes with netsh, but 
other than being ugly as well, it's not platform independent solution.



What I would require is (if it's somehow possible), to make the 
platform-independent client do prefix discovery, find the prefix 
on-link, but do not configure routing information for that link. And to 
do it the proper way.

Any ideas?