Re: IPv6, was IPv10 (fwd)

Brian E Carpenter <> Thu, 29 December 2016 19:54 UTC

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Subject: Re: IPv6, was IPv10 (fwd)
To: John R Levine <>, IETF general list <>
References: <alpine.OSX.2.11.1612291429570.37525@ary.qy>
From: Brian E Carpenter <>
Organization: University of Auckland
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Date: Fri, 30 Dec 2016 08:54:40 +1300
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On 30/12/2016 08:30, John R Levine wrote:
>>> I might be able to use ULAs but I have no idea how well ULAs actually work
>> Exactly like any other global-scope IPv6 address. They just work. (I speak
>> from experience.)
> How do I tell my router that the ULAs on the home side of the router are 
> different from ULAs on the cableco side?

Your ULAs are all in your ULA /48 prefix. I'm not clear why the cableco would
be using ULAs, but if they do, those address will be in the cableco's ULA /48.
No confusion is possible, and as a border router, it SHOULD drop outbound
packets with source addresses in your ULA /48.

>> If you want static addresses on your servers, it's no different from any 
>> other static address. But maybe I am not understanding your concern.
> If I knew I had an address range that held still, I would use DHCPv6 and see 
> how many of my devices handle it.  What happens if I have ULA addresses handed 
> out by DHCPv6 and global addresses from SLAAC?  Do I have to turn off SLAAC?

In the router advertisements, the prefix information option for the ULA prefix
would need its A flag turned off.

> (If this stuff is all written down somewhere, I would be thrilled to get 
> the reference.)

This is more for v6ops or even To be honest I
don't know if any of the IPv6 books covers this stuff in detail.