@David-TP Hi David, thanks!

They saw the configuration above and don't see a reason why it wouldn't work. They said:

1. PPPoE login/passwords is the same for IPv4

2. VLAN needs to be setup the same as well (848)

3. that it should be enough to have IPv6 DHCP switched on and then prefix delegation should work

That's it. Should I ask for something specific?

Note that I am having "pair bonding" in front of Deco (https://support.zyxel.eu/hc/en-us/articles/360014415759-VMG4005-B50A-and-Pair-Bonding-), if that makes a difference.

  @kotrfa try turning the iptv/vlan off and see if that works as it should just go through without issues unless you using iptv?

I send logs to the support (under a different account)

I found out that when turning on IPv6, it keeps getting an address for a brief period and then losing it or getting a new one. Internet works (for like loading a single page, e.g. 3 seconds), and then goes down. The IPv4 connection also gets "blank" and no IP address is shown there until it gets it again. E.g. this is a sequence after watching it for like 4 minutes:

Hey. I got new credentials from my ISP and now I am not in an endless loop anymore, but it still doesn't work. Here is the log from the unit. What's interesting is that I can see it actually get the IP prefix (look for "2bcd:6222:2:2:1:<MY-OBFUSCATED-IPv6-ADDRESS>:/62"), but it fails in the end. The first weird thing I found in the log is at lines 128-135, exiting on few lines later with no valid ipv6 address found:

invalid prefix length 62 + 16 + 64

Is it possible that Deco X60 doesn't handle prefix of to me assigned IPv6 address /62? I know the default value is usually /64 and it can be changed in some TP-Link devices (such as this one), but there is no such setting in Deco.