RTA52i Rev.4.01.11 (Mon Nov 6 23:00:07 2000)
# MAC Address : 00:a0:de:0a:4e:f6
# Memory 8Mbytes, 1LAN, 1BRI
login password *
administrator password *
isdn local address ??????????
ip filter 1 reject * * udp,tcp 135,netbios_ns-netbios_ssn *
ip filter 2 reject * * udp,tcp * 135,netbios_ns-netbios_ssn
ip filter 3 restrict * * tcpfin * www,ftp,nntp
ip filter 4 restrict * * tcprst * www,ftp,nntp
ip filter 10 reject 192.168.0.0/24 * * * *
ip filter 11 pass * 192.168.0.0/24 icmp * *
ip filter 12 pass * 192.168.0.0/24 established * *
ip filter 13 pass * 192.168.0.0/24 tcp,udp * domain,ident
ip filter 14 pass * 192.168.0.0/24 tcp ftpdata *
ip filter 15 pass * 192.168.0.0/24 udp domain *
ip filter 40 pass * 192.168.0.4 tcp * www
ip filter 41 pass * 192.168.0.4 tcp * smtp
ip filter 42 pass * 192.168.0.4 tcp * ntp
ip filter 43 pass * 192.168.0.4 udp * ntp
ip filter 100 pass * * * * *
ip filter source-route on
ip filter directed-broadcast on
ip lan address 192.168.0.1/24
ip lan routing protocol none
ip lan secure filter in 1 2 100
ip route default gateway pp 1 metric 1
nat descriptor type 1 masquerade
nat descriptor masquerade static 1 1 192.168.0.4 tcp www
nat descriptor masquerade static 1 2 192.168.0.4 tcp smtp
nat descriptor masquerade static 1 3 192.168.0.4 tcp ntp
nat descriptor masquerade static 1 4 192.168.0.4 udp ntp
provider type isdn-terminal
pp select 1
pp name PRV/1/1/0:asahi-net
isdn remote address call ??????????
isdn auto disconnect off
ip pp secure filter in 10 11 12 13 14 15 40 41 42 43
ip pp secure filter out 3 4 100
ip pp nat descriptor 1
pp auth accept pap chap
pp auth myname ?????????@atson.net ?????????
ppp ipcp ipaddress on
pp enable 1
provider set on 1 asahi-net
provider dns server 1 202.224.32.1 202.224.32.2
provider select 1
dhcp scope 1 192.168.0.2-192.168.0.254/24
dns server 202.224.32.1 202.224.32.2
dns private address spoof on

pptp host lan
operation connect 1

ブラウザ上で簡単に設定できました。IPフィルター関係はオプションで設定します。
Webサーバー,メールサーバー,タイムサーバー用ポートにアクセスを許可し、
静的NATマスカレードにてサーバーIPアドレスをそれぞれ指定。