Reproducing:
vyos@vyos# set interfaces pppoe pppoe0 authentication password 'test' vyos@vyos# set interfaces pppoe pppoe0 authentication user 'test' vyos@vyos# set interfaces pppoe pppoe0 source-interface 'eth1' vyos@vyos# commit [edit] vyos@vyos# run show interfaces pppoe Codes: S - State, L - Link, u - Up, D - Down, A - Admin Down Interface IP Address S/L Description --------- ---------- --- ----------- pppoe0 100.64.0.9/32 u/u [edit] vyos@vyos# set interfaces pppoe pppoe0 disable [edit] vyos@vyos# commit [edit] vyos@vyos# run show interfaces pppoe Codes: S - State, L - Link, u - Up, D - Down, A - Admin Down Interface IP Address S/L Description --------- ---------- --- ----------- pppoe0 100.64.0.9/32 u/u