icmpを通さない設定になっているはずなのですが、pingを打つと返ってきます。
どこが悪いかわからないので、configみてもらえないでしょうか。

# RT58i Rev.9.01.41 (Fri Feb 20 17:00:51 2009)
# MAC Address : 00:a0:de:51:06:e2, 00:a0:de:51:06:e3
# Memory 32Mbytes, 2LAN, 1BRI
# main: RT58i ver=c0 serial=N1M190297 MAC-Address=00:a0:de:51:06:e2 MAC-Addres
s=00:a0:de:51:06:e3
# Reporting Date: May 20 19:06:59 2009
console prompt RT58i
login timer 1200
ip route default gateway pp 1
ip lan1 address 192.168.100.254/24
ip lan1 secondary address 122.1.1.1/29
ip lan1 secure filter in 1000 1001 1100
provider lan1 name LAN:
pp select 1
pp always-on on
pppoe use lan2
pppoe auto connect on
pppoe auto disconnect off
pp auth accept pap chap
pp auth myname hoge hoge
ppp lcp mru on 1454
ppp ccp type none
ip pp mtu 1454
ip pp secure filter in 1000 1001 1300 1200
ip pp secure filter out 1000 1001 1100 dynamic 500 501 502 503 504 505 506
ip pp nat descriptor 1
ip pp tcp mss limit auto
pp enable 1