Windows 10 (1903) clinets not keeping IPv6 Gateway
I sent already a request to the Zyxel support but no answer from there. Maybe someone here in the Forum can help.
Imagine following situation:
Using a Zywall USG60 with several VLANs bond to LAN1 for internal LAN separation. The ISP is connected to WAN1. To get ISP traffic working it was needed to configure a VLAN on top of WAN1 and on top of the VLAN a PPP interface. From the provider the USG gets an IPv6 prefix (/56) via DHCPv6. The prefix is delegated using Prefix delegation to the single VLANs each which it's own amendment to the prefix. So far so good.
I enabled the router advertisement on those internal VLANs to announce the IPv6 router to the clients. Those fe80::xxxxxx addresses stay in the Windows clients for about three minutes then they just vanish with the result no IPv6 traffic towards other VLANs nor the internet is possible anymore. When disabling and enabling the interface on the Windows client the three minutes stars again.
There's no problem with Apple Mac and iOS devices. They keep the router information as it should.
Any idea what could be the reason?
Firmware version on my USG60 is: 4.33(AAKY.0). SLAAC is disabled on all interfaces.
Thank you already for some help.