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In a case I can use only UDP and ICMP protocols, how can I discover, in bytes, the path MTU for packet transfer from my computer to a destination IP?

  • Do you want to solve this programmatically or with ping? Ping and either shell programming or combined with traceroute are options for example. Also do you want ipv4 or ipv6? – Max Dec 30 '12 at 17:46
  • @Max: shell programming it sounds good , have an idea for that ? – URL87 Dec 30 '12 at 17:58
  • 2
    I thought about using ping -s $SIZE -c 1 -M dont and lowering that SIZE value till it works, or just having a look at the ICMP returns via tcpdump if we are talking ipv6 but traceroute has this built in I just realized. – Max Dec 30 '12 at 18:06
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I believe what you are looking for, is easiest gotten via traceroute --mtu <target>; maybe with a -6 switch thrown in for good measure depending on your interests. Linux traceroute uses UDP as a default, if you believe your luck is better with ICMP try also -I.

17

A quick search with apropos mtu on CentOS5 turned out:

tracepath traces path to a network host discovering MTU along this path

This command even works unprivileged in user space.

  • I prefer this over traceroute since it returns a simple result at the end and I don't have to look for the last hop that returned a different MTU. – comfreak Aug 14 '17 at 17:22

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