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

[Christian Huitema <[e-mail]>]

On 2/5/2019 11:46 AM, Lee Howard wrote:

>
> And yet when somebody says "I built my network for reasons that were
> compelling to me at the time" you tell them they did it wrong. It's
> tiresome. 


+1. I am always amazed at how long threads can become on the IPv6
mailing list. It seems that the problem is rather simple:

1) For some reason, the router gets reconnected, and the new connection
comes with a different IPv6 prefix.

2) At that point, all IPv6 addresses allocated to hosts on the network
become stale, and may remain so for some potentially long time.

3) We want to transition rapidly to a new state in which hosts acquire
addresses based on the new prefix and can communicate again.

Lots of the discussion centers on denial. "Don't worry about that, the
router's prefix should not change." Really? There are tons of scenarios
in which stuff happens, such as for example a router dialing up a back
up cellular connection if the land line connection broke. Or the various
events in which the back-haul network configuration changes. These
events are obviously painful, as all existing TCP connections are going
to break. The providers probably strive to make them rare, because
inflicting pain on customers is not a great business plan. But rare does
not mean "never". Denying that is going to cause tons of frustration.

-- Christian Huitema