Crappy ISP router, wanted my own router doing everything with IPv6, this is what worked

Tried almost everything. IPv4 dual-NAT was easy (I wanted to set my router to do everything, so in the future I can potentially change ISP or better, have dual-wan access but all homelab stuff stays on the same IP range).

IPv6 was a pain (why not to have that too for the fun), tried a lot of settings, putting here what worked:

• ISP / Yallo router: Stateless (IPv6 cannot be disabled, only seem to have one /64 prefix (no proper /56 or separate /64), cannot go to bridge mode)
• TP-Link router (Archer AX73):
  • IPv6 WAN: Dynamic IP connection, Prefix Delegation Enabled, Custom DNS Servers
  • IPv6 LAN: ND proxy
• Seems to work and clients get the custom DNS
• With SLAAC on TP-Link LAN config clients got two sets of IPv6 addresses (two RAs) and clearly there was a routing issue as all applications took and eternity to load (probably they went back to IPv4 after failing on IPv6)

What did not work:

• stateful ISP IPv6 + anything on my router
• anything else on my router (router invented a second prefix... but it was probably not delegated)

Hereby I would like thank Claude Max getting me up to IPv6 a bit.

Tested on Win 10, Win 11, Ubuntu 24 LTS, Android

ISP: Yallo (Switzerland), super CGNAT router. Cannot do bridge, cannot disable IPv6, it's a piece of work

I hope this will post help others in the future (as I could not find so comprehensive posts).

What do I use IPv6 for? Totally nothing. But after my initial trials it turned out IPv6 DNS servers burn into Win11, found no way to clear them, even if the NI does not have IPv6 address... Did not want to disable IPv6 as portable devices might need it... when ported... so was easier to fix it.