ICMP Types

Answered Question
Oct 16th, 2007
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Hi all,


I would like to know what is decimal equvalent for ICMP type ttl-exceeded?


Some of them I could use as:


0 - for echo-reply

8 - for echo

11 - for time-exceeded


I know that I can use syntax as:


permit icmp any any ttl-exceeded


but I would like to know what is decimal equvalent for it.


Best regards,

Vladimir


Correct Answer by dominic.caron about 9 years 7 months ago

That's type 3 code 4

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dominic.caron Tue, 10/16/2007 - 04:46
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I dont think ttl-exeeded type exist.


ttl-exceeded is (TYPE 11,CODE 0)


ICMP message have a code field (8bit) that can give you further info.


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vnovakov Tue, 10/16/2007 - 06:08
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Thanks for quick answer!, Does it mean than that:


permit icmp any any ttl-exceeded


will allow only ICMP packets type 11 with code O and


permit icmp any any time-exceeded


will allow all ICMP type 11 with code 0 or 1?


Am I correct?


I have found a way how to add rules as ICMP type and code:


permit icmp any any 11

permit icmp any any 11 0

permit icmp any any 11 1


will apear as:


permit icmp any any time-exceeded

permit icmp any any ttl-exceeded

permit icmp any any reassembly-timeout


Also I'm confused with packet-to-big. By RFC 1885 it is Type 2 Code 0. But under Cisco ISO 12.4:


permit icmp any any 2 0


rule will not apear as:


permit icmp any any packet-too-big


am I wrong about packet-too-big icmp type and code that is used by Cisco?


regards,

Vladimir


Correct Answer
dominic.caron Tue, 10/16/2007 - 07:09
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That's type 3 code 4

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