/etc/npppd/npppd.conf:

    /etc/npppd/npppd.conf 
    tunnel PPPOE protocol pppoe {
      listen on interface cpsw0
      lcp-keepalive yes
      lcp-keepalive-interval 60
      lcp-keepalive-retry-interval 30
      lcp-keepalive-max-retries 40
      lcp-timeout 3
      debug-dump-pktin lcp
      authentication-method pap
    }
    authentication LOCAL type local {
        users-file "/etc/npppd/npppd-users"
    }
    ipcp IPCP {
        dns-servers 8.8.8.8
    }
    bind tunnel from PPPOE authenticated by LOCAL to pppx0


/etc/hostname.cpsw0:

    up


/etc/sysctl.conf:

    net.pipex.enable=1


???(idk):

    inet 0.0.0.0 255.255.255.255 NONE \
      pppoedev cpsw0 authproto pap \
      authname '12345678@isp.net' authkey 'abcd1234' up
    dest 0.0.0.1
    #inet6 eui64
    !/sbin/route add default -ifp pppoe0 0.0.0.1
    #!/sbin/route add -inet6 default -ifp pppoe0 fe80::%25pppoe0


???:

    /etc/npppd/npppd.conf:19: interface pppx0 is not found