Re: A common problem with SLAAC in "renumbering" scenarios

Michael Richardson <mcr+ietf@sandelman.ca> Wed, 20 February 2019 15:29 UTC

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From: Michael Richardson <mcr+ietf@sandelman.ca>
To: Mikael Abrahamsson <swmike@swm.pp.se>
cc: Mark Smith <markzzzsmith@gmail.com>, Fernando Gont <fgont@si6networks.com>, 6man WG <ipv6@ietf.org>
Subject: Re: A common problem with SLAAC in "renumbering" scenarios
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Date: Wed, 20 Feb 2019 10:29:30 -0500
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Mikael Abrahamsson <swmike@swm.pp.se> wrote:
    >> - By default, hosts don't delete addresses from interfaces if the
    >> interface goes down. Addresses persist across interface down/up
    >> events. If the most common cause of hosts' interfaces going down and
    >> coming back up was considered to be attachment to a different link,
    >> then addresses would probably be deleted by default upon link down.

    > This is no longer true. If you install a Windows machine, ubuntu desktop
    > (with networkmanager, which is the default), MacOS, Android, iOS, they ALL
    > take the addresses away when there is a link-down.

By link-down, do you mean cable pulled out, or "ifconfig eth0 down"?
Annoyingly, Linux flushes all IPv6 addresses on ifconfig-down, but leaves the
IPv4 there, and you have to "ifconfig eth0 inet 0.0.0.0" to get rid of it.

I actualy would like the LL addresses to remain and just become very lossy on
link down, as that would allow the network to flap while not loosing a
mgmt ssh connection in over fe80:...%eth0 address.

--
Michael Richardson <mcr+IETF@sandelman.ca>, Sandelman Software Works
 -= IPv6 IoT consulting =-