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Date: Wed, 02 Feb 2000 09:57:03 +0900
From: Masachika ISHIZUKA <ishizuka@ish.org>
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Subject: [FreeBSD-users-jp 49476] Re: Directed broadcast
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  $B@PDM!w?yJB$G$9!#(B

  directed broadcast $B$K$D$$$F65$($F$/$@$5$$!#(B
  NIC $B$r(B2$BKg:9$7$F(B gateway_enable="YES" $B$7$FF0$+$7$F$k%^%7%s(B
$B$KBP$7$F!"$b$&(B1$BKg$N(B NIC $B$N(B directed broadcast $B$KBP$7$F(B ping
$B$rBG$D$H!"1~Ez$,Mh$k$N$G$9$,!"(Bipfw $BEy$G(B filtering $B$9$k0J30(B
$B$K$3$l$r;_$a$k<j$O$J$$$N$G$7$g$&$+!#(B

  $BNc$($P!"0J2<$N7O$r:n$k$H!"$3$&$J$j$^$9!#(B

+------+              +------+              +------+
| PC-1 +--------------+ PC-2 +--------------+ PC-3 |
+------+              +------+              +------+
       a              b      c              d

a: 192.168.1.2/24
b: 192.168.1.1/24
c: 192.168.2.1/24
d: 192.168.2.2/24

(1) PC-1 $B$+$i(B 192.168.1.0 $B$X(B ping
  $BL51~Ez(B

(2) PC-1 $B$+$i(B 192.168.1.255 $B$X(B ping
  $BL51~Ez(B

(3) PC-1 $B$+$i(B 192.168.2.0 $B$X(B ping
  b $B$,(B Destination Host Unreachable $B$rJV$9(B

(4) PC-1 $B$+$i(B 192.168.2.255 $B$X(B ping
  c $B$,(B ping $B$KEz$($k(B

  net.inet.icmp.bmcastecho = 0 $B$J$N$G!"(B(1), (2) $B$O;_$^$k(B
$B$N$G$9$,!"(B(4) $B$O$A$g$C$HJQ$@$H;W$&$N$G$9$,!"$3$l$r(B ipfw
$BEy$N(B packet filtering $B$rMQ$$$J$/$F$b;_$a$k$3$H$O$G$-$J$$(B
$B$N$+$rCN$j$?$$$N$G$9!#(B
  $B$G$-$l$P!"(B(3) $B$bL51~Ez$K$G$-$k$H4r$7$$!#!J(Bsmurf $B967b4X(B
$BO"$NOCBj$,!":#:"$K$J$C$F$^$?(B janog ML $B$J$s$+$rFx$o$;$F$$(B
$B$k$N$G!"$A$g$C$H5$$K$J$C$?$b$N$G!#1~Ez$9$k%"%I%l%9$O(B1$B8D(B
$B$@$1$GJ#?t$G$O$J$$$N$G!"JL$KLdBj$J$$$C$F$$$&8+J}$b$G$-$k(B
$B$H$O;W$$$^$9$,!"$=$l$G$O(B net.inet.icmp.bmcastecho = 0 $B$C(B
$B$F2?$J$s$@$!$C$F$$$&5$$b$7$A$c$&$b$N$G!#!K(B

  PC-2 $B$O(B FreeBSD 3.4-RELEASE $B$G$9!#!J(B3.3-RELEASE $B$G$bF1(B
$B$8$G$7$?!#!K(Brouting $B$K0MB8$9$k$N$+$H;W$C$F!"(Bstatic routing
$B$H(B ospf + gated $B$r<B83$7$F$_$^$7$?$,!">I>u$OF1$8$G$7$?!#(B

  $B59$7$/$*4j$$CW$7$^$9!#(B
