Problems with IPV6 Masquerading, no connectivity until I ping router

[cmspam]

My situation is as follows. I have an IPV6 /64 subnet from my ISP. Generally I can use ND-Proxy in order to access IPV6 from my devices behind the router.

Running latest stable OpenWrt 22.03.3 r20028-43d71ad93e

When I set everything up with ND-Proxy, it works fine.

I want to enable IPV6 Masquerading in order to use mwan3.

I run the commands from the wiki:

uci set firewall.@zone[1].masq6="1"
uci commit firewall
/etc/init.d/firewall restart

It works great. Until I reset the router or add a new machine. When that happens, the device gets an IPV6 address, but I can't ping anything outside the LAN. Once I ping the router's public IPV6 address, connectivity is restored for that machine (Maybe it found the route at that point?) and it works on that machine until I restart the router again.

I want to use this on devices like game consoles, so I can't ping the router every time the device comes up.

The symptoms are very similar to this post

IPv6 only works after pinging the router

Router have no route rules until my client ping the router's ipv6 address. Here is my network setting /etc/config/network config interface 'loopback' option ifname 'lo' option proto 'static' …

Can anyone tell me where to look?

[cmspam]

I managed to solve it by using two /65 prefixes, one for the WAN and one for the LAN, disabling SLAAC. Having a /64 prefix is really bad, indeed