Re: Non routable IPv6 registry proposal

Keith Moore <> Thu, 11 March 2021 16:48 UTC

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Subject: Re: Non routable IPv6 registry proposal
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From: Keith Moore <>
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Date: Thu, 11 Mar 2021 11:48:52 -0500
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On 3/11/21 5:22 AM, Nico Schottelius wrote:

>> Another question I have is whether such ULA allocations
>> will realistically remain local.
> ULAs are unlikely staying local, as we have seen with radio networks in
> Germany. Tunnels are being used to interconnect remote cities and
> non-collision (not necessarily public routing) are a primary concern.

Despite the name, there's no reason that ULAs should stay local.   As 
long as they are properly chosen, it's perfectly reasonable to route 
them privately between cooperating networks, and IMO this is part of 
their design.   One of the problems with RFC 1918 addresses in IPv4 was 
that enterprises had a need to route traffic between networks each using 
that space.   The resulting address collisions generally required 
explicit NAT configurations to work around, and these were failure-prone 
and difficult to manage.  ULAs were intended in part to remedy this problem.