Re: [v6ops] draft-ietf-v6ops-64share

Michael Richardson <mcr+ietf@sandelman.ca> Tue, 30 July 2013 16:20 UTC

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Date: Tue, 30 Jul 2013 12:19:02 -0400
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Cc: IPv6 Ops WG <v6ops@ietf.org>
Subject: Re: [v6ops] draft-ietf-v6ops-64share
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cb.list6 <cb.list6@gmail.com> wrote:
    mcr> I don't understand.
    mcr> Why does adding a second IP address change anything that is already alive?

    > It should not, i agree.  So, i am a little confused by your question.

    > Scenario 1 moves the prefix from WAN to LAN, this may break an open connection.

Ah, I understand, the operation of moving the prefix, if done as break before
make, which is required sometimes, might kill connections.

    > Scenario 2 replicates the IP on 2 interfaces

    > Are you suggesting that we simply keep the /128 on the WAN and put the
    > /64 on the LAN with normal SLAAC and new LAN inteface IP?  The issue
    > with that, is that on the LAN, the /128 on the WAN is not accounted
    > for and may cause a conflict / duplicate, so it is easier to make the
    > WAN and LAN intefaces IP the same

I wonder if this is really true.
I know that Linux, by default, with a weak host model, will answer IPv4 ARP
for interface 2, when asked for it on interface 1. (Many think this is a bug,
even a security bug, and there are options in 2.6.8-ish to disable that)

I will try the same thing with DAD. I have a test bench where this will be easy.
I imagine it ought to fail, but I could be wrong.  It is something that could
be fixed if desired.  I don't know what the specification say, and if
weak/strong host model was even taken into account here.

--
Michael Richardson <mcr+IETF@sandelman.ca>, Sandelman Software Works