IPv6 on LAN not torn down if IPv6 on WAN gone

Technical Support for Routers
1

I have two SIMs for my hotspot, both of which do IPv6, so I enable it and it works (I use “NAT6” on the LAN when using mobile data).

But if I switch to a WAN w/o IPv6 (i.e., many hotel Ethernets) while the IPv6 toggle is on, the WAN side still thinks it’s got an IPv6 address, so the LAN side continues to advertise (RD?) the ULA for the NAT6 (fd15:: ) so devices on the LAN think they can still route IPv6, and fail. See below for a screenshot of what it looks like after switching from an IPv6 dual-stack connection to an IPv4-only connection.

I guess- I’m not exactly sure- but perhaps when Interfaces change and IPv6 is enabled, to tear it down and let it come back up if the WAN advertises IPv6? I can fix this by toggling IPv6 off then disconnecting/reconnecting each client device, but that’s pretty unwieldy.

Screenshot_20220607_110913001

2

BTW, this is today’s Stable 4.0.0 release (but it’s been happening since the beginning).

3

@dengxinfa can you check this issue?

4

In the nat6 mode, the ipv6 address of the LAN is assigned by the router (br-lan).

Therefore, the LAN obtains ipv6 regardless of whether the WAN has ipv6.

5

Sure, I understand - but without IPv6 on the WAN, IPv6 on the LAN via NAT6 is now unroutable- and also, as you see in the screenshot, the AX still thinks it still has a working IPv6 address even though it no longer exists (I’ll check to see via ssh if this is just a UI bug, but should be fixed in any case).

Could we just tear down/remake LAN IPv6 on WAN changes? That seems best, IMO.