Firstly, you need
ip4forwarding=yesat /etc/rc.cnf. It is "yes" by default for adslrouter model.
To use PPPoE (RP-PPPoE), specify
pppoe=yesat /etc/rc.conf and prepare files at /etc/ppp/ directory properly. "pppoe" is "yes" by default for adslrouter model.
To make /etc/ppp/ configurations, it is useful to use /usr/pkg/sbin/adsl-setup on other NetBSD host which has rp-pppoe. You can install rp-pppoe from pkgsrc.
Copyright (C) 1993-2018 Ken'ichi Fukamachi mail:< fukachan at fml.org >