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From: Mitani Hiroshi <hmitani@vrl.mei.co.jp>
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Subject: [IPv6-jp 1035] Path MTU discovery
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$B$O$8$a$^$7$F!">>2<EE4o$N;0C+$H?=$7$^$9!#(B

FreeBSD-4.5R $B$r%k!<%?$,$o$j$K$7$F!"(BPath MTU Discovery $B$r%F%9%H$7$F(B
$B$$$^$9!#$=$3$GIT;W5D$J8=>]$,=P$^$7$?$N$G65$($F2<$5$$!#(B


$B%k!<%?$N9=@.$O!"(BIntel $B$N(B Gigabit Ethernet $B$N#2Kg;I$7$G!"%I%i%$%P$O(B
em $B$r;H$C$F$$$^$9!#(Bv4 $B$H(B v6 $B$NN>J}$N%"%I%l%9$r?6$C$F$$$^$9!#$^$?!"(B
rtadvd em0 em1 $B$H$7$F!"%5%$%H%m!<%+%k$N%"%I%l%9$r3d$j?6$k$h$&$K$7$F(B
$B$$$^$9!#(B

$BC<Kv$O!"(BRedHat Linux $B$G!"$=$3$G(B tracepath6(iputils)$B$r;H$$$^$7$?!#(B

1)MTU $B$r(B 1500-->1400-->1500 $B$HJQ2=$5$;$?>l9g(B

$B%k!<%?$N#2Kg(B(em0, em1)$B$N(B MTU $B$r(B ifconfig $B$G(B 1500-->1400-->1500 $B$H(B
$B@_Dj$7$F!"FC$KLdBjL5$/F0$-$^$9!#(B

2)MTU $B$r(B 1500-->800-->1500 $B$HJQ2=$5$;$?>l9g(B

MTU $B$,(B 800 $B$N>uBV$G$O!"(Bv6 $B$ODL$i$J$$$N$G$9$,!"(Bv4 $B$N%k!<%?$H$7$F$O(B
$BF0$$$F$$$^$9!#$o$+$i$J$$$N$O!"(BMTU $B$r:F$S(B 1500 $B$KLa$7$?$H$-$G$9!#(B
$B$3$N;~!"(Bping6 -s 1400 $B$ODL$j$^$9!#$,!"%5%$%:$,(B 1400 $B$N(B UDP $B%Q%1%C%H(B
$B$O!"%k!<%?$rDL2a$G$-$^$;$s!#$7$+$b!"2?$N(B ICMP $B$b%k!<%?$+$i%=!<%9B&(B
$B%[%9%H$K$OJV$C$FMh$J$$$N$G$9!#(B

  tracepath6 $B$O:G=i$K!"(BICMP echo request $B$rEj$2$F!"FO$/$h$&$J$i!"(B
  udp $B%Q%1%C%H$r%5%$%:$r(B 1500 $B$+$i=y!9$K>.$5$/$7$F!"Aj<j$N;H$C$F(B
  $B$$$J$$%]!<%H$KEj$2!"(BICMP unreach $B$,JV$C$FMh$k$^$GD4$Y$^$9!#(B


$B$=$3$G65$($F$$$?$@$-$?$$$N$O!'(B

a. MTU $B$r(B 800 $B$K@_Dj$7$?$H$-!"%k!<%?$N5sF0$O$I$&$"$k$Y$-$+(B?
$B%k!<%F%#%s%0$G$-$J$$$K$b4X$o$i$:!"(Brtadvd $B$O1F6A$r<u$1$:$KF0$$$F$$$k(B
$B$h$&$G$9!#$=$l$O$=$&$$$&$b$N$J$s$G$7$g$&$+(B?

b. 1500 $B$KLa$7$?8e!"(Bping6 $B$ODL$k$,!"(Budp $B$O>C<:$9$k$N$O$J$<$+(B?
$B$5$i$K!"$J$K$+$,(B expire $B$5$l$k$N$rBT$D!"$"$k$$$O!"@Q6KE*$K(B flush $B$9(B
$B$l$P!"$b$H$N>uBV$KLa$k$N$G$7$g$&$+(B?

$B$h$m$7$/$*4j$$$7$^$9!#(B
--
                                   $B>>2<EE4o;:6H(B($B3t(B) AVC$B<R(B AVC$B3+H/%;%s%?!<(B
                                          $B;0C+(B $B9@(B   hmitani@vrl.mei.co.jp
