Re: [v6ops] Scope of Unique Local IPv6 Unicast Addresses (Fwd: New Version Notification for draft-gont-6man-ipv6-ula-scope-00.txt)

Michael Richardson <mcr+ietf@sandelman.ca> Sat, 13 February 2021 03:53 UTC

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From: Michael Richardson <mcr+ietf@sandelman.ca>
To: IPv6 Operations <v6ops@ietf.org>, "6man\@ietf.org" <6man@ietf.org>
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Date: Fri, 12 Feb 2021 22:53:49 -0500
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Subject: Re: [v6ops] Scope of Unique Local IPv6 Unicast Addresses (Fwd: New Version Notification for draft-gont-6man-ipv6-ula-scope-00.txt)
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Ted Lemon <mellon@fugue.com> wrote:
    > On Feb 12, 2021, at 6:12 PM, Fernando Gont <fgont@si6networks.com>
    > wrote:
    >> Both the uniqueness scope and the routing scope of ULAs are smaller
    >> than that of GUAs.

    > This is true, but the distinction is that there is no automatic
    > mechanism specified for knowing whether a particular ULA is in scope
    > for a link. It’s perfectly valid to use the default route to forward to
    > a ULA destination. If a host were to automatically not do this, things
    > would break all over the place.

Agreed.

And the potential leak is now by default much less as the DHCPv6-PD mechanism in
OpenWRT creates SADR default routes that look like:
   from 2001:db8:1234::/48 default via dev ...

plus, of course, ISP use of BCP38.

    > IOW, what Fred said is perfectly correct and sensible, but the sense in
    > which ULAs are global is that you should (MUST?) use the default route
    > to route them unless there is a more specific route that matches.

+1

--
Michael Richardson <mcr+IETF@sandelman.ca>   . o O ( IPv6 IøT consulting )
           Sandelman Software Works Inc, Ottawa and Worldwide