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

[Philip Homburg <[e-mail]>]

>There are also DHCP servers that can be configured to always find the 
>oldest expired lease and hand that out if there are no never-used 
>resources. If a device shows up 2 months after the lease expired with the 
>same DUID and nobody has used that lease in between, then they get the 
>same PD again that they had 2 months prior.
>
>If the device has permanent storage then it could ask for the previous PD 
>it had, and if that's free then it'd get it. So as discussed earlier in 
>the thread, having the HGW just store the last PD it had could be helpful 
>even if it never updates it with information as long as it's the same.

The problem starts when the ISP wants to change prefixes. As far as I know,
there is no documentation on how that should be done. I also think it is 
unlikely that the majority will get it right.

If the device has permanent storage then it can also announce the old prefix
with preferred and valid lifetimes set to zero. However that doesn't work
when a CPE vendor doesn't want to write that information to flash storage.