Re: [v6ops] DHCPv6/SLAAC Make Hosts Confusing-//RE: new draft: draft-liu-bonica-v6ops-dhcpv6-slaac-problem

"Weil, Jason" <> Tue, 29 October 2013 19:59 UTC

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From: "Weil, Jason" <>
To: Mark ZZZ Smith <>, "Liubing (Leo)" <>, Wuyts Carl <>, "" <>
Date: Tue, 29 Oct 2013 15:59:40 -0400
Thread-Topic: [v6ops] DHCPv6/SLAAC Make Hosts Confusing-//RE: new draft: draft-liu-bonica-v6ops-dhcpv6-slaac-problem
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Subject: Re: [v6ops] DHCPv6/SLAAC Make Hosts Confusing-//RE: new draft: draft-liu-bonica-v6ops-dhcpv6-slaac-problem
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I wasn't claiming it was a problem that a host has two addresses. I was
just saying it might be beneficial in certain scenarios for all hosts on a
network segment (SLAAC-only, SLAAC+DHC, DHC-only) to have a single address
created using the same algorithm.


On 10/29/13 3:28 PM, "Mark ZZZ Smith" <> wrote:

>----- Original Message -----
>> From: "Weil, Jason" <>
>> To: Liubing (Leo) <>om>; Wuyts Carl
>><>>; "" <>
>> Cc: "" <>rg>; ""
>> Sent: Wednesday, 30 October 2013 1:44 AM
>> Subject: Re: [v6ops] DHCPv6/SLAAC Make Hosts Confusing-//RE: new draft:
>> Leo,
>> First I wanted to say this is useful work and I support it.
>> This topic in this email reminds me of an issue that we have run across
>> that might be relevant to your draft:
>> The use case involves a home network whose gateway router sets M=1 and
>> in order to provide DHC and and SLAAC for hosts that do not implement a
>> DHC client. If the DHCPv6 Server is implementing IP assignment using
>> interface-identifier and using the same prefix as advertised in the PIO
>> (assuming the server resides on the router advertising the PIO) with
>>the A
>> bit set, hosts that support SLAAC and a DHCPv6 client could construct
>> same address using DHC as the one they construct using SLAAC. What is
>> clear is what hosts should do in this situation. IMO, there is a benefit
>> if hosts that support both SLAAC and DHCPv6 construct the address and
>> prefer the DHC address over the SLAAC address. The benefit is that you
>> reduce the number of active addresses and all hosts end up with a single
>> address per prefix administered in this fashion.
>> Of course if your DHC Server implements another assignment algorithm
>> Random) then your hosts that support both may end up with 2 addresses
>> of the same prefix.
>Another way to describe your scenario is that it is a transition scenario
>between SLAAC and stateful DHCPv6, since some of your hosts don't support
>stateful DHCPv6.
>In your scenario, I don't think it is a big problem that some of your
>hosts will have two addresses within the same prefix - IPv6 hosts are
>designed to cope with many addresses, and a /64 has plenty of addresses
>to go around.
>If you do want to be specifically selective about which hosts use SLAAC
>and which hosts use stateful DHCPv6 for addressing, use host specific RAs
>which set the M and the PIO A bits on a selected host basis.

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