Please Whitelist This Site?

I know everyone hates ads. But please understand that I am providing premium content for free that takes hundreds of hours of time to research and write. I don't want to go to a pay-only model like some sites, but when more and more people block ads, I end up working for free. And I have a family to support, just like you. :)

If you like The TCP/IP Guide, please consider the download version. It's priced very economically and you can read all of it in a convenient format without ads.

If you want to use this site for free, I'd be grateful if you could add the site to the whitelist for Adblock. To do so, just open the Adblock menu and select "Disable on tcpipguide.com". Or go to the Tools menu and select "Adblock Plus Preferences...". Then click "Add Filter..." at the bottom, and add this string: "@@||tcpipguide.com^$document". Then just click OK.

Thanks for your understanding!

Sincerely, Charles Kozierok
Author and Publisher, The TCP/IP Guide


NOTE: Using software to mass-download the site degrades the server and is prohibited.
If you want to read The TCP/IP Guide offline, please consider licensing it. Thank you.

The Book is Here... and Now On Sale!

Get The TCP/IP Guide for your own computer.
The TCP/IP Guide

Custom Search







Table Of Contents  The TCP/IP Guide
 9  TCP/IP Lower-Layer (Interface, Internet and Transport) Protocols (OSI Layers 2, 3 and 4)
      9  TCP/IP Internet Layer (OSI Network Layer) Protocols
           9  Internet Control Message Protocol (ICMP/ICMPv4 and ICMPv6)
                9  ICMP Message Types and Formats
                     9  ICMP Version 4 (ICMPv4) Error Message Types and Formats

Previous Topic/Section
ICMP Version 4 (ICMPv4) Error Message Types and Formats
Previous Page
Pages in Current Topic/Section
1
2
34
Next Page
ICMPv4 Source Quench Messages
Next Topic/Section

ICMPv4 Destination Unreachable Messages
(Page 2 of 4)

ICMPv4 Destination Unreachable Message Format

Table 88 and Figure 139 show the specific format for ICMPv4 Destination Unreachable messages.


Table 88: ICMPv4 Destination Unreachable Message Format

Field Name

Size (bytes)

Description

Type

1

Type: Identifies the ICMP message type; for Destination Unreachable messages this is set to 3.

Code

1

Code: Identifies the “subtype” of unreachable error being communicated. See Table 89 for a full list of codes and what they mean.

Checksum

2

Checksum: 16-bit checksum field for the ICMP header, as described in the topic on the ICMP common message format.

Unused

4

Unused: 4 bytes that are left blank and not used.

Original Datagram Portion

Variable

Original Datagram Portion: The full IP header and the first 8 bytes of the payload of the datagram that prompted this error message to be sent.



Figure 139: ICMPv4 Destination Unreachable Message Format

 


Previous Topic/Section
ICMP Version 4 (ICMPv4) Error Message Types and Formats
Previous Page
Pages in Current Topic/Section
1
2
34
Next Page
ICMPv4 Source Quench Messages
Next Topic/Section

If you find The TCP/IP Guide useful, please consider making a small Paypal donation to help the site, using one of the buttons below. You can also donate a custom amount using the far right button (not less than $1 please, or PayPal gets most/all of your money!) In lieu of a larger donation, you may wish to consider purchasing a download license of The TCP/IP Guide. Thanks for your support!
Donate $2
Donate $5
Donate $10
Donate $20
Donate $30
Donate: $



Home - Table Of Contents - Contact Us

The TCP/IP Guide (http://www.TCPIPGuide.com)
Version 3.0 - Version Date: September 20, 2005

Copyright 2001-2005 Charles M. Kozierok. All Rights Reserved.
Not responsible for any loss resulting from the use of this site.