tracereroute fragmentation

[burhanburhan]

Hi all,

Is there any way to understand if fragmentation happening or not by traceroute command ?

[Mark Malone]

standard traceroute just shows latency in hops and what ips your passing , tracepath in Linux is one that can show you fragmentation , so below if I got reduced along path it would show beside the ms and state at the end the mtu , but below shows it hasn't been reduced anywhere along path

xxxxxxxxxxx:~$ tracepath -n 172.21.229.65
 1?: [LOCALHOST]                                         pmtu 1500
 1:  172.22.160.252                                        0.505ms
 1:  172.22.160.252                                        0.460ms
 2:  172.22.253.5                                          0.573ms
 3:  172.22.251.6                                          2.555ms
 4:  172.22.254.62                                         2.783ms
 5:  172.22.254.244                                        0.728ms
 6:  x.x.x.x                                           2.652ms
 7:  x.x.x.x                                          207.948ms asymm 19
 8:  172.21.254.254                                      210.249ms asymm 17
 9:  172.21.254.41                                       210.915ms asymm 17
10:  172.21.253.5                                        208.501ms reached
     Resume: pmtu 1500 hops 10 back 17

[burhanburhan]

and is there a command to see this output at cisco routers ? or windows pc ?

[Mark Malone]

if you doing it form cisco you can test the lowest path through ping in cli using ping .. size and then keep dropping size until you find the lowest mtu on path between src-dst that's useable

mturoute for windows should do the same

http://www.elifulkerson.com/projects/mturoute.php

[burhanburhan]

Ok thank you Mark.