> For example, you can (today) sign up for two (or more!) ISPs that support IPv6 Prefix Delegation and have your router(s) issue Router Advertisements (RAs) for each prefix.
As a user of OpenWrt (which does exactly this) I strongly disagree that it is the right solution. If you announce on the LAN the prefixes obtained from a fast fiber and a slow LTE link, then devices will, well, get an address for each prefix. The problem is that they have absolutely no information to choose the source address correctly - it's all just numbers! So, just by bad luck, they choose the source address from the LTE prefix and waste the LTE data and my money if I use the default setup. Which is why I don't. My network uses IPv6 NPT, but announcing one prefix at a time would have been even better (because I only want fail-over, not real multihoming), although impossible with OpenWrt.
As a user of OpenWrt (which does exactly this) I strongly disagree that it is the right solution. If you announce on the LAN the prefixes obtained from a fast fiber and a slow LTE link, then devices will, well, get an address for each prefix. The problem is that they have absolutely no information to choose the source address correctly - it's all just numbers! So, just by bad luck, they choose the source address from the LTE prefix and waste the LTE data and my money if I use the default setup. Which is why I don't. My network uses IPv6 NPT, but announcing one prefix at a time would have been even better (because I only want fail-over, not real multihoming), although impossible with OpenWrt.
Forum discussion, which also serves as a proof that it is really hard to explain the "don't overcomplicate fail-over by generalizing it to multi-homing" notion: https://forum.openwrt.org/t/ipv6-wan-fail-over-without-ipv6-...