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As written in the RFC 791 this option is useful to record the addresses of the routers that an ip datagram goes through.

I'm sending an ip datagram with an ICMP echo message, i've set the option type (of the header ip) on 7, the option length on 7 and the pointer on 4.

I expect an echo reply with the first router address to come back, but this doesn't happends. Am i doing something wrong or the option is not supported anymore?(If i don't set the options, the echo response comes back as expect)

  • AFAIK it is not that it not supported "anymore" but rather, it has never been supported (on the Internet). Most routers simply ignore the option (as well as many other options). – JFL Jun 13 '17 at 12:12
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    RFC 791 is 36 years old and this option has never been adopted. – Zac67 Jun 13 '17 at 17:01
  • @Zac67, JFL Thank you both, i wasn't sure but you confirmed my doubts – PoBeLe Jun 13 '17 at 18:43
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Strictly about question: It works as stated by RFC791, as you have figured.

"I expect an echo reply with the first router address to come back, but this doesn't happends."

If you are doing this out on the wild, as it's you on your computer pinging some random IP from the Internet, it won't work as this is considered a security vulnerability and hence likely moderated by ISP's/others.

Such risk can be seen for example Cisco Security ICMP Record Route vulnerability

To test this feature you will probably need to have your own devices/images, regardless of the intended OS to get this setting working.

Real life usage for 'record route' can be seen in RSVP for MPLS.

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RFC 791 is 36 years old and this option has never been adopted.

Please mark this question as answered or it'll keep popping up.

  • This is not an answer. – Peter Green Jun 14 '17 at 13:00
  • No, it isn't - but this site should have some people able to mark an abandoned question as answered. Any use for single-visit user's questions popping up years later? – Zac67 Jun 14 '17 at 17:53
  • I've included the answer from the comment. – Zac67 Jun 14 '17 at 18:51
  • Nice to see you're still with us! ;-) – Zac67 Jun 14 '17 at 21:33

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