I'm a complete noob at IPv6, but have some practical experience of IPv4 (just because I had to deal with it).
My home router is behind CGNAT so they don't offer public IPv4 addresses, but I'd asked about getting an IPv6 address and my ISP has kindly provided me with one. In their reply they said my address is
2a01:XXXX:XXXX:4000::/56. Reading about it, I got the idea that I can and should provide my network devices with GUAs which is kind of appealing to me.
Behind my ISP's router I've got a OpenWRT one for educational purposes. All my other devices are behind the latter. In order to properly run DHCP my OpenWRT needs to get a prefix from my ISP's router (that is DHCPv6 enabled as well).
My confusion comes about the
/56 at the end of the address. I guess network masks don't make sense for GUAs so is that the delegated prefix that I can use for my private network? If so when assigning the prefix to my OpenWRT router should I narrow it down in case I decide to have more devices behind my ISP's router in the future?
How can I validate that the whole thing works as expected? My ISP's router has a crappy UI and no console, I can see the GUA having been assigned but not the
/56 (which I won't put a name on because I'm not sure what it's called yet). My OpenWRT assigns addresses to hosts based on its global ULA settings which means its not taking into account whatever prefix the other router may be publishing (if it even works properly).
The ISP router has a checkbox to enable prefix delegation based on the WAN settings (which is checked) and another section for static prefixes which is empty atm.