Failover IPv6 with multiple PA prefixes (Was: IPv6 fc00::/7 - Unique local addresses)

Tim Franklin tim at
Tue Nov 2 05:51:44 CDT 2010

>> Your home gateway that talks to your internet connection can either
>> get it via DHCP-PD or static configuration. Either way, it could
>> (should?) be set up to hold the prefix until it gets told something
>> different, possibly even past the advertised valid time.
> That breaks the IPv6 spec. Preferred and valid lifetimes are there
> for a reason.

And end-users want things to Just Work.  The CPE vendor that finds a hack that lets the LAN carry on working while the WAN goes away and manages to slap the "With Home Network Resilience!" label on the box correctly will presumably do quite nicely out of it.

For this kind of site, I can't see what is *actually* going to break if the CPE keeps sending RAs for the prefix beyond the valid lifetime while the WAN is down.  As long as it advertises a short valid lifetime itself, such that if the real prefix changes[0] when the WAN comes back up it can renumber everything on the LAN quickly, it looks a lot like a "Just Works" scenario to me...


[0] Which it won't, of course, because residential users are going to get proper static connections by default, rather than another round of "business class" price-gouging :)

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