How to get public IP to Ubuntu 20.04?

suvas

I am trying to get a public IP with a direct Ethernet cable from modem to the system (no router in between) and it's failing to create pppoe interface. I have given right credentials that my ISP provided in /etc/ppp/chap-secrets and following right steps to setup DSL.
I am receiving this chap-secrets authentication error in ppp logs and not able to get the public IP.

I followed these steps, but no luck.
https://askubuntu.com/questions/966647/how-to-create-a-dsl-connection-in-network-manager-in-ubuntu-17-10

ffox

Not all combinations of DSL-modem and ISP allow such type of login necessarily.