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ICMP extensions RFC

Recently-published RFC 5837 describes additions to ICMP messages that would allow you to gather more information (including interface ifIndex, IP address and name). Two obvious applications are enhanced traceroute and path MTU discovery where the new ICMP extensions could indicate which interface is the MTU bottleneck.

The RFC authors come from BT, Juniper and Cisco, so there’s a non-zero chance it will actually get implemented where it’s most needed.


  1. Why do I get the feeling that this will just be more protocols that either -
    1) have to be blocked by policy/regulation, or
    2) get blocked randomly mid-path, making them somewhat unreliable as troubleshooting tools

    I'm constantly reminding people that ping and traceroute aren't universally allowed, thus are often unreliable troubleshooting tools outside of the local boundary.

  2. Ivan Pepelnjak27 April, 2010 10:55

    This is not a new protocol, it's another option in the ICMP reply packet. Nothing more to block (apart from the SP deciding whether to include the information in the replies or not).

    Anyhow, I guess this was targeted more at troubleshooting end-to-end path across a single management domain (I doubt you'd want to give this information to your competitor).


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Ivan Pepelnjak, CCIE#1354 Emeritus, is an independent network architect. He has been designing and implementing large-scale data communications networks as well as teaching and writing books about advanced technologies since 1990. See his full profile, contact him or follow @ioshints on Twitter.