Re: [v6ops] ULA and IPv4 - draft-liu-v6ops-ula-usage-analysis

Tim Chown <> Tue, 05 November 2013 02:59 UTC

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From: Tim Chown <>
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Date: Tue, 5 Nov 2013 02:58:50 +0000
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Subject: Re: [v6ops] ULA and IPv4 - draft-liu-v6ops-ula-usage-analysis
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The 3484’s in that chunk of text should be 6724’s.


On 5 Nov 2013, at 02:50, Christopher Palmer <> wrote:

> Section 3.3 of the draft:
> “  As described in section 2.2.2 of [RFC5220], when an enterprise has
>    IPv4 Internet connectivity but does not yet have IPv6 Internet
>    connectivity, then the enterprise chose ULA for site-local IPv6
>    connectivity. Each employee host will have both an IPv4 global or
>    private address and a ULA. Here, when this host tries to connect to
>    an outside node that has registered both A and AAAA records in the
>    DNS, the host will choose AAAA as the destination address and the ULA
>    for the source address according to the IPv6 preference of the
>    default address selection policy [RFC3484]. This will clearly result
>    in a connection failure.”
> This is only true if the ULA is configured on a host that also has a default route The enterprise can avoid any issues by simply configuring a scoped route on hosts (say, only for the ULA prefix). If a network does not provide connectivity to the IPv6 Internet, it should not advertise ::/0.
> I think it’s useful to discuss that configuration route, which is possible today with a vast majority of hosts and just works.
> Modifying the prefix policy table is not suitable at scale. And the DNS preference logic alluded to in section 3.3 is highly ambiguous.
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