Re:Tell HN: IPv6-only still pretty much unusable
by zekica on Wednesday December 07, 2022 @01:02PM
(#33897738)
The correct way to do this is to advertise the fiber connection's prefix to devices on LAN as long as that connection is available. When it fails, the router should send RA with zero as the expiry time for that prefix, and include the LTE prefix. This way, all devices will immediately start using the new prefix. You can use ULA in addition so local connections don't fail.
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Re:Tell HN: IPv6-only still pretty much unusable
by patrakov on Wednesday December 07, 2022 @01:11PM
(#33897839)
This can work with the fiber + LTE example, and with the rat example, but does not cover the "modem crash" example. The ADSL modem does not know its old prefix, and thus cannot send zero-expiry-time announcements for it.
Also consider a case where there is an ADSL modem (with the ISP giving out /56 via prefix delegation) and a home lab with virtual machines, that are behind a virtualization host, which grabs a subprefix (let's say a /64, separate from the main home LAN /64 prefix) for its VMs from the modem via DHCPv6. While there is indeed a mechanism for flash renumbering over SLAAC, which may work for devices in the home LAN, there is also a need to invalidate the subprefix delegated for virtual machines via DHCPv6 through the virtualization host. Last time I checked, this is not implemented anywhere.