IPv6 over ppp autoconfiguration not working in squeeze

[Adam Spragg <adam@spra.gg>]

Hi Debian IPv6 list,

I've been trying to get IPv6 working on and off for a while now, and I just 
can't get it working.

My Debian Squeeze box is my home server/router/firewall, connected via a 
Speedtouch modem to the internet. It's been working with IP4 fine for ages. My 
ISP has assigned me IPv6 block 2001:4d48:ad51:300::/56 and assured me it 
should "just work".

I've added the following lines to my /etc/ppp/options:

    +ipv6
    ipv6cp-accept-local

and set the sysctl parameter

    net.ipv6.conf.all.accept_ra=2

I am getting an IPv6 address on ppp0 since adding the ppp options, but it's 
the local fe80::/10 address, not the one assigned by my ISP. I've used 
tcpdump/wireshark to confirm I am receiving ICMPv6 neighbour advertisements 
and router advertisements. (Although the prefix information they contain is 
for 2001:4d48:ad00:5103::?)

My /etc/network/interfaces stanza for ppp0 is simply:

    iface ppp0 inet ppp
        provider myisp
        post-up /etc/network/firewall

I've thought about configuring the address statically, but can't figure out 
how to do it. "address" does not appear to be an option for "ppp" stanzas. 
I've tried setting it in the /etc/ppp/peers/myisp file with

    ipv6 2001:4d48:ad51:300::1

but just get:

    /usr/sbin/pppd: Illegal interface identifier (local):
        2001:4d48:ad51:300::1

when I try to bring the interface up. Plus, this is supposed to be automatic, 
right?

I've read <http://wiki.debian.org/DebianIPv6> and most of the links on there, 
and just can't figure out what I might be doing wrong. Anyone any ideas how I 
go about debugging this further?


Thanks,

Adam