>>610
PPPoE Unnumbered接続なら

pp select 1
pp keepalive use lcp-echo
pp always-on on
pppoe use lan2
pppoe auto connect on
pppoe auto disconnect off
pp auth accept chap
pp auth myname ID PASSWORD
ppp lcp mru on 1454
ip pp mtu 1454
pp enable 1

これでヒントのつもりなんだけど、どうかねぇ？