Dear Alexey,

30 Jun 21 05:24, you wrote to me:

 VS>>>> I know that my home router can advertise multiple global IPv6
 VS>>>> prefixes into the LAN, but how will LAN hosts failover to the
 VS>>>> backup gateway if the primary ISP fails? They will have IPv6
 VS>>>> addresses from both blocks, which should they choose for their
 VS>>>> outgoing src address?
 AV>>> This is the preferred mode of operation, but it has (only) two
 AV>>> disadvantages: 1. All hosts in the LAN must be able to do the
 AV>>> switching|balancing on thy own (that means, run Linux; the
 AV>>> BSD-style networking stack, like the one used in Windoze, has
 AV>>> very limited functionality). 2. This may require some manual
 AV>>> configuration on every of them. Not really a problem, but may
 AV>>> be boring.
 VS>> This is not feasible because most of those LAN hosts are
 VS>> smartphones, smart TVs, vacuum cleaners, cameras and other IoT
 VS>> devices.

 AV> Most of these devices have Linux kernel, but crippled userspace.

 VS>>>> With two IPv4 ISPs and NAT, the setup is rather trivial,
 VS>>>> outgoing connections will work via either of the ISPs because
 VS>>>> the hosts needn't be aware of the failure, and their src
 VS>>>> private IP is always the same. Can anyone enlighten me?
 AV>>> This is second option, but you'd lose the main advantage of
 AV>>> IPv6: the use of publicly routed addresses.
 VS>> Indeed. I don't like the idea of using NAT in IPv6 even if I
 VS>> could. So what's the solution?

 AV> For dumb devices, especially portable, I'd suggest using NPT.

How well does NPT (being stateless) work with FTP, SIP and other protocols which embed addresses into payload?

 AV> Fully
 AV> functional computers may be connected to some other VLANs (two at once
 AV> in your case) and configured to use real addresses.

Speaking of those fully functional computers in the LAN, do you mean the setup when there is a script pinging some outside hosts/interfaces and modifying the IPv6 routing table, or something more advanced and interesting?

Victor Sudakov, VAS4-RIPE, VAS47-RIPN
--- GoldED+/BSD 1.1.5-b20170303-b20170303