Cisco LAC/LNS question

Frank Bulk - frnkblk at
Fri Dec 31 22:05:36 CET 2010

Thanks, Daniel, this is now coalescing in my mind.  I knew there was
something special about IPv6 and IPCP, but this example makes it concrete
for me.

Once I get this working with the Cisco 871W I'm testing with, then I'm off
to try with the D-Link 615 and 825, as well as a couple of DSL modems I have
on my counter.


-----Original Message-----
From: at
[ at] On Behalf Of
Daniel Roesen
Sent: Friday, December 31, 2010 8:12 AM
To: ipv6-ops at
Subject: Re: Cisco LAC/LNS question

On Thu, Dec 30, 2010 at 05:25:54PM -0600, Frank Bulk - wrote:
> Why in the virtual-template section is there a
>   peer default ip address dhcp
> but no
>   peer default ipv6 address dhcp

Because IETF decided to not include global IP negotiation in IP6CP
in PPP. IP6CP only negotiates an interface identifiers which are then
used to create link-local addresses on both ends. Determination of
the global addresses is then supposed to happen with SLAAC or DHCPv6.

> The only thing I can do is
>   peer default ipv6 pool <poolname>
> which uses a local pool on the BRAS.

That's for a local prefix delegation pool. See

> I would like to use an external DHCP server to hand out the PPP client
> addresses.  I believe "ipv6 dhcp relay destination <servername>" is only
> prefix delegation.

Not really, also for global IP.

If you need to assign "known" IPv6 global addresses to PPP clients,
you need to make them do DHCPv6 for it. One way is to send RAs on the
PPP session with managed config flag set.

Best regards,

CLUE-RIPE -- Jabber: dr at -- dr at IRCnet -- PGP: 0xA85C8AA0

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