Re: Radvd and prefix delegation
Jason White <jason@jasonjgw.net> writes:
> My (static) IPv6 prefix is assigned by my ISP via DHCPv6 prefix delegation.
> Currently, the radvd init script is configured to start during boot so as to
> advertise over the eth0 interface. The problem this creates, however, is that
> radvd starts before wide-dhcpv6-client assigns an address to eth0.
>
> Aug 31 06:58:12 jdc radvd[3671]: no auto-selected prefix on interface eth0,
> disabling advertisements
>
> One solution would be to start radvd in /etc/ppp/ipv6-up.d/somescript but
> there may be better ways.
>
> I am trying to avoid actually specifying the address anywhere in the
> network configuration, so that if a different prefix is ever advertised,
> everything will still work. I don't expect my ISP to change its address
> allocation, and if that did happen I would still need to update the DNS
> entries, but reducing the dependencies in the configuration still has an
> advantage.
Yes, having some way to signal DNS server config to radvd without
rewriting the config would be nice. But I don't think you need to
expect the DNS config to change even if the prefix changes, or did I
misunderstand something? ISPs rarely have any reason to renumber their
DNS servers, except if they want to test their customer support under
full load :-)
> How have others chosen to deal with this?
I simply call
/etc/init.d/radvd reload
in a /etc/ppp/ipv6-up.d/somescript. In theory you should be prepared
for a prefix change anytime the link goes down, so I believe this is
necessary even if you modify the initial start order.
But you are of course correct that most sane ISPs will give you the same
prefix every time you connect. There are however reasons why an ISP may
want to renumber a set of subscribers, so it's always best to be
prepared for such renumbering.
Bjørn
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