ping at MTU=1500

Asked by Guy Fearenside

I want to be able to ping at an MTU (maximum transmission unit) value of 1500 to test for fragmentation problems in the network, Is this possible with the Network Tools software?

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marcobra (Marco Braida)
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Best marcobra (Marco Braida) (marcobra) said :
#1

Please use the ping command...

Open a Terminal from the menu Applications → Accessories → Terminal and type:

ping -s packetsize ip_address

http://ubuntuforums.org/showthread.php?t=872346

Hope this helps

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Guy Fearenside (g-fearenside) said :
#2

Thanks for the reply, I also talked to a friend who also suggested this and gave me more info.
I can use "nslookup" to cover DNS to IP address and vice versa:

desktop:~$ nslookup bbc.co.uk
Server: 192.168.1.254
Address: 192.168.1.254#53

Non-authoritative answer:
Name: bbc.co.uk
Address: 212.58.224.138

==============================
It is possible to ping and specify the MTU with "-s 1500" and also the number of pings with "-c 5" for 5 pings.
If the MTU value of the router is exceeded there is no reply, so "Control + C" to stop the pings and back to the prompt.

desktop:~$ ping -c 5 -s 1400 bbc.co.uk
PING bbc.co.uk (212.58.224.138) 1400(1428) bytes of data.
1408 bytes from virtual-vip.thdo.bbc.co.uk (212.58.224.138): icmp_seq=1 ttl=114 time=72.6 ms
1408 bytes from virtual-vip.thdo.bbc.co.uk (212.58.224.138): icmp_seq=2 ttl=114 time=71.2 ms
1408 bytes from virtual-vip.thdo.bbc.co.uk (212.58.224.138): icmp_seq=3 ttl=114 time=72.2 ms
1408 bytes from virtual-vip.thdo.bbc.co.uk (212.58.224.138): icmp_seq=4 ttl=114 time=70.8 ms
1408 bytes from virtual-vip.thdo.bbc.co.uk (212.58.224.138): icmp_seq=5 ttl=114 time=71.4 ms

--- bbc.co.uk ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4000ms
rtt min/avg/max/mdev = 70.830/71.703/72.653/0.690 ms

===============================

There is a manual built in Terminal which gives all the options availabe to any command:

man ping
Press keys "Control + C" to come out of the manual and back to the terminal prompt, "space bar" to move down the page of the manual:

PING(8) System Manager’s Manual: iputils PING(8)

NAME
       ping, ping6 - send ICMP ECHO_REQUEST to network hosts

SYNOPSIS
       ping [-LRUbdfnqrvVaAB] [-c count] [-i interval] [-l preload] [-p pattern] [-s packet‐
       size] [-t ttl] [-w deadline] [-F flowlabel] [-I interface] [-M hint] [-Q tos] [-S
       sndbuf] [-T timestamp option] [-W timeout] [hop ...] destination

DESCRIPTION
       ping uses the ICMP protocol’s mandatory ECHO_REQUEST datagram to elicit an ICMP
       ECHO_RESPONSE from a host or gateway. ECHO_REQUEST datagrams (‘‘pings’’) have an IP
       and ICMP header, followed by a struct timeval and then an arbitrary number of ‘‘pad’’
       bytes used to fill out the packet.

OPTIONS
       -a Audible ping.

       -A Adaptive ping. Interpacket interval adapts to round-trip time, so that effec‐
              tively not more than one (or more, if preload is set) unanswered probes
              present in the network. Minimal interval is 200msec for not super-user. On
              networks with low rtt this mode is essentially equivalent to flood mode.

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Guy Fearenside (g-fearenside) said :
#3

Thanks marcobra, that solved my question.

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Guy Fearenside (g-fearenside) said :
#4

Sorry its :q to quit from the manual:

There is a manual built in Terminal which gives all the options availabe to any command:

man ping
Press keys ":q" to come out of the manual and back to the terminal prompt, "space bar" to move down the page of the manual, "Carriage return" to go down a line at a time.