No IPv6 to Connected Devices When USB Tethering to Router

[hrawat]

So in our area, there's no 5G & Jio's 4G works really well.

Now I have a cheap phone which I use for hotspots using Jio 4G sim. I get 35-40 Mbps speed when using hotspot and 65-70 Mbps speed when using USB Tethering.

Now since MacOS doesn't support USB Tethering and the phone's inbuilt hotspot has low range & slow speed as it has 2.4G 20MHz hotspot. So I purchased TP-Link Archer C6U router and installed OpenWrt in it and connected my phone using USB Tethering. Now my Laptop and other phones are getting 70+ Mbps speed.

Current Setup:
Jio 4G SIM in Phone > Connected to Router Using USB Tether > Router connected to other Phone & Laptops via WiFi & LAN.

Now everything works well but the router interface was getting IPv6 and I could ping IPv6 address using the router but devices connected using Router don't get IPv6 address, they work in IPv4 mode only.

After searching online, I enabled IPv6 Relay mode and now my mobile gets IPv6 address for some time then stops getting it until I reconnect it while on my Mac I'm still unable to get an IPv6 address.

There's some issue with Jio issue /128 & /64 IPv6 prefix as per what I understood after looking on the internet. What could be a possible workaround?

 

[hrawat]

How do I enable SLAAC mode in openwrt? In TP-Link stock firmware, there's option for it.

 

[alap4m]

It appears there's a breakdown in IPv6 when using RNDIS or the OpenWrt equivalent of USB Tethering.
You might have to forgo it because it seems Jio could be limiting such connections to IPv4.
As for enabling SLAAC in OpenWrt, it is called "Auto-generated random address", according to this link.
Moreover, according to this page, "Per default, SLAAC and both stateless and stateful DHCPv6 are enabled on an interface."