ipv6, stateful config and non-default prefixlen

[Eugene M. Zheganin]

  Hi.

I'm trying to get a working freebsd workstation with an ipv6 network 
where addresses are received from DHCP.
ATM my IPv6 setup copies the IPv4 layout with vlans and /24 masks, so 
I'm using /120 prefixes.
Is that even possible ?
As the Handbook lacks any information about such setup, I decided to ask 
for help here.

Currently I'm having problems with prefixes.
I'm using the net/isc-dhcp41-client port (as the dhclient from the base 
system is unable to work with DHCPv6).
I have a working rtadvd on a router, and a working DHCPv6 setup.
But my client FreeBSD still gets  64 prefix length, with or without 
running rtsold.
Since DHCPv6 doesn't advertise any routing information at all (including 
the prefix information), and its only function is to provide the client 
with an address, I assume that the prefix information has to be received 
from the router advertisements. I am currently looking at the wireshark 
dump, and it appears that my workstation is receiving such 
advertisements. However it doesn't affect the 64 prefix displayed in 
ifconfig, and all operation involving the nodes outside the actual link 
are simply not working.

Also I want to say that other operating systems on the same link are 
working properly (for example they can exchange with nodes in other 
networks).

Thanks.