Use of unique local IPv6 addressing rfc4193

Ryan, Spencer sryan at
Fri Sep 9 00:58:49 UTC 2016

I agree with Karl.

We use the ULA space for our internal test labs. The /48's we have in use get routed around internally but have no chance of leaking to the internet.

Spencer Ryan | Senior Systems Administrator | sryan at<mailto:sryan at>
Arbor Networks
+1.734.794.5033 (d) | +1.734.846.2053 (m)<>

From: NANOG <nanog-bounces at> on behalf of Karl Auer <kauer at>
Sent: Thursday, September 8, 2016 8:49:34 PM
To: nanog at
Subject: Re: Use of unique local IPv6 addressing rfc4193

On Thu, 2016-09-08 at 23:43 +0000, Pshem Kowalczyk wrote:
> both ways - if we decide to use it we'll have to either overlay it
> with public IPv6 space (and provide the NAT/proxy for where we don't
> have any public IPv6 assigned) or simply not use the fc00::/7 and
> skip the NAT/proxy aspects of it.

There is no necessary link between ULA addresses and NAT. You don't
have to NAT ULA, *ever*. If you need public addresses, go get them.
There are enough.

IMHO one should use ULA in only three situations:

- a completely isolated network
- for internal communications e.g. fabric management)
- for testing

Regards, K.

Karl Auer (kauer at

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