wongabu

BGP is not for everyone: get an ASN, your own prefixes, and run BGP. Compare that to the simplicity of ipv4 NAT.

Ipv6 NAT66 is fundamentally broken, see sibling comment.

Have you tried it? NAT66 implies using fd00::/8, which then gets deprioritized in all devices below ipv4, in accordance with RFC 3484. The end result: all devices revert to using ipv4 on dual stack lan.

Ipv6 is fundamentally broken for failover scenarios.

Ipv4 does NOT have this problem. The typical setup is always NAT for ipv4 lan, so external address can be changed with minimal disruption.

All ipv4 apps that require hole punching assume they will need to "discover" the external address anyways, for every new p2p connection.

In contrast to the vast majority of ipv6 apps which assume their ipv6 address is identical to external ipv6 address, as this is(was) the main marketing point of ipv6 - directly addressable end points.

That's one ugly hack, which assumes (1) WAN1 has static ipv6 (the typical SME has dynamic DHCPv6 address...) (2) all the devices will behave correctly when running on NPT on failover WAN2. Many devices do not know about NPT which is basically NAT for ipv6, and break on p2p protocols like voice, video, streaming. They'll send the wrong NPT address to the other side, which try to connect back to the WAN1 address, which is down because of failover.

There is no working solution to ipv6 dual WAN failover, 30 years later... A critical design flaw that was simply ignored by the designers despite being used in almost any SME network.

inb4 no you can't have all lan devices have multiple ipv6 addresses and choose for themselves, typically 1 WAN is cheap and the second WAN is expensive/slow and should be used only for WAN1 failover

Inb4 no you can't just advertise new RA, devices on lan can takes minutes to update.

On ipv4, NAT+changing route on router just works, 1-2 seconds failover.