I recently configured my ERL WAN Interface as a PPPoE and connected it to the carrier modem (Fiber to Ethernet) directly. Here is a config to update the DDNS for Namecheap
Replace including < > with the corresponding part of your DDNS details.
set service dns dynamic interface pppoe0 service namecheap host-name <your host name NOT domain name>
set service dns dynamic interface pppoe0 service namecheap login <your domain ie abc.com>
set service dns dynamic interface pppoe0 service namecheap password <password-check under namecheap ddns section>
set service dns dynamic interface pppoe0 service namecheap server dynamicdns.park-your-domain.com
Hope this helps.
