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

Christopher Morrow morrowc.lists at
Mon Nov 1 11:17:53 CDT 2010

On Mon, Nov 1, 2010 at 5:28 AM, Mark Smith
<nanog at> wrote:
> On Sun, 31 Oct 2010 21:32:39 -0400
> Christopher Morrow <morrowc.lists at> wrote:
>> On Sun, Oct 31, 2010 at 3:10 PM, David Conrad <drc at> wrote:
>> > On Oct 31, 2010, at 6:45 AM, Christopher Morrow wrote:
>> >>>> "If Woody had gone straight to a ULA prefix, this would never have happened..."
>> >>> Or better yet, if Woody had gone straight to PI, he wouldn't have this problem, either.
>> >> ula really never should an option... except for a short lived lab, nothing permanent.
>> >
>> > Seems to me the options are:
>> >
>> > 1) PI, resulting in no renumbering costs, but RIR costs and routing table bloat
>> > 2) PA w/o ULA, resulting in full site renumbering cost, no routing table bloat
>> > 3) PA w/ ULA, resulting in externally visible-only renumbering cost, no routing table bloat
>> >
>> > Folks appear to have voted with their feet that (2) isn't really viable -- they got that particular T-shirt with IPv4 and have been uniformly against getting the IPv6 version, at last as far as I can tell.
>> >
>> > My impression (which may be wrong) is that with respect to (1), a) most folks can't justify a PI request to the RIR, b) most folks don't want to deal with the RIR administrative hassle, c) most ISPs would prefer to not have to replace their routers.
>> >
>> > That would seem to leave (3).
>> >
>> > Am I missing an option?
>> I don't think so, though I'd add 2 bits to your 1 and 3 options:
>> 1) we ought to make getting PI easy, easy enough that the other
>> options just don't make sense.
> Surely your not saying "we ought to make getting PI easy, easy enough
> that the other options just don't make sense" so that all residential
> users get PI so that if their ISP disappears their network doesn't
> break?

all the world is not a corner case... I don't think sane folks are
supportive of 'every end site gets pi', I think it's somewhat sane to
believe that enterprise type folks can/should be able to get PI space
to suit their needs. ULA for enterprises is really not a good

Cable/dsl end users can certainly apply for PI space they may even be
able to justify an allocation (see owen...) I don't think they'll have
much success actually getting a DSL/Cable provider to actually hold
the route for them though... so I'm not sure that your pathological
case matters here.


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