Archer C6 V3 is here

[Deleted member 83050]

@anmolbhard004 that's what i asked you to change earlier . Change it to SLAAC+ Stateless DHCP

 

[anmolbhard004]

@rajat_ aisa koi option hi mujhe nahi dikh raha. 🙁 🙁

Source

 

[anmolbhard004]

@rajat_ is it due to the router?

 

[Deleted member 83050]

Prefix delegation is automatically set. It is usually /64 prefix of global IPv6 address. This is an assignment problem for sure because your router is getting a global IP from PPPoE.
I have had similar issue in the past. You can refer to this thread.