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

Ted Lemon <> Fri, 12 February 2021 23:30 UTC

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From: Ted Lemon <>
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Date: Fri, 12 Feb 2021 18:29:52 -0500
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Cc: Fred Baker <>, IPv6 Operations <>, "" <>
To: Fernando Gont <>
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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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On Feb 12, 2021, at 6:12 PM, Fernando Gont <> 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.

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.