Re: Node Requirements: Elevating DHCPv6 from MAY to SHOULD

Mohacsi Janos <mohacsi@niif.hu> Tue, 31 May 2011 10:10 UTC

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Date: Tue, 31 May 2011 12:10:11 +0200
From: Mohacsi Janos <mohacsi@niif.hu>
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To: Markus Hanauska <hanauska@equinux.de>
Subject: Re: Node Requirements: Elevating DHCPv6 from MAY to SHOULD
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On Tue, 31 May 2011, Markus Hanauska wrote:

>
> On 2011-05-31, at 11:19 , Philip Homburg wrote:
>
>
> My main problem with that approach is, that not everyone has a $5000++ 
> Cisco router available and the configuration capabilities of some more 
> inexpensive routers are quite limited; especially regarding IPv6, which 
> is still not mainstream (the majority of routers on the market still has 
> no IPv6 support at all). Also what are you going to do, if your ISP only 
> gives you a single /64 prefix? To subdivide it, you have to use some 
> bits for subnetworking, which means your hosts might only have /48 
> addresses and that disables SLAAC entirely.

If you get /64 and you need more subnets from your provider then probably 
you asked something wrong.
You should get /64 if and only if you have only one subnet! Or your ISP 
does not understand IPv6. In this case avoid it.

>
> I still think it would have been much easier, to define a second bit in 
> the /64 address space. Just like the 'u' bit, which says that an address 
> is globally unique or not, there would be the 'a' bit, which is set if 
> the address has been assigned "automatically" (SLAAC w/ or w/o Privacy 
> Extension) and not set, if this address has been "manually" assigned 
> (either by manual config on the node or by DHCP or anything comparable 
> to DHCP). This will effectively eliminate collisions, except for MAC 
> address collisions or collisions caused by misconfiguration of manual 
> IPs and/or DHCP.
>

What collision? You should use 'u' bit accrdingly:
1 - if automaticaly assigned
0 - if manually assigned.

Best Regards,
 		Janos Mohacsi