Icmp V4 And Icmp V6

Unit 2 Of ACN

1. ICMP v4 and ICMP v6

2. ICMP overview
•Delivery method of IP is
–connectionless, unreliable and unacknowledged.
•In TCP/IP, diagnostic, test and error-reporting
functions at the internet/network layer are
performed by the Internet Control Message
Protocol (ICMP)
•ICMP is the Internet Protocol’s “administrative
assistant”.
•The original version, now called ICMPv4, is used
with IPv4, and the newer ICMPv6 with IPv6.

3. ICMP General operation

4. Limitations
•ICMP error-reporting messages can only
be sent back to the originating device.
–Intermediate devices cannot be the recipient
of an ICMP message
–Because their addresses are normally not
carried in the IP datagram’s header.

5. ICMP messages
•ICMP messages are divided into two general
categories:
–error messages that are used to report problem
conditions
–informational messages that are used for diagnostics,
testing and other purposes.
•Total 256 messages each for ICMPv4 &
ICMPv6.
•In ICMPv4 there is no relationship between Type
value and message type
•In ICMPv6 error messages have a Type value of
0 to 127, informational messages 128 to 255.

6. ICMPv4 Error messages
•Type Value: 3
•Message Name : Destination Unreachable
•Summary of Message Type:
–Indicates that a datagram could not be delivered
to its destination. The Code value provides more
information on the nature of the error.

7. ICMPv4 Error messages
•Type Value: 4
•Message Name : Source Quench
•Summary of Message Type:
–Lets a congested IP device tell a device
that is sending it datagrams to slow down
the rate at which it is sending them.

8. ICMPv4 Error messages
•Type Value: 5
•Message Name : Redirect
•Summary of Message Type:
–Allows a router to inform a host of a better
route to use for sending datagrams.

9. ICMPv4 Error messages
•Type Value: 11
•Message Name : Time Exceeded
•Summary of Message Type:
–Sent when a datagram has been discarded
prior to delivery due to expiration of its
Time To Live field.

10. ICMPv4 Error messages
•Type Value: 12
•Message Name : Parameter Problem
•Summary of Message Type:
–Indicates a miscellaneous problem
(specified by the Code value) in delivering
a datagram.

11. ICMPv4 Informational messages
•Type Value: 0
•Message Name : Echo Reply
•Summary of Message Type:
–Sent in reply to an Echo (Request)
message; used for testing connectivity.

12. ICMPv4 Informational messages
•Type Value: 8
•Message Name : Echo (Request)
•Summary of Message Type:
–Sent by a device to test connectivity to
another device on the internetwork. The
word “Request” sometimes appears in the
message name.

13. ICMPv4 Informational messages
•Type Value: 9
•Message Name : Router Advertisement
•Summary of Message Type:
–Used by routers to tell hosts of their
existence and capabilities.

14. ICMPv4 Informational messages
•Type Value: 10
•Message Name : Timestamp (Request)
•Summary of Message Type:
–Sent by a device to request that another
send it a timestamp value for propagation
time calculation and clock
synchronization. The word “Request”
sometimes appear in the message name.

15. ICMPv4 Informational messages
•Type Value: 8
•Message Name : Echo (Request)
•Summary of Message Type:
–Sent by a device to test connectivity to
another device on the internetwork. The
word “Request” sometimes appears in the
message name.

16. ICMPv4 Informational messages
•14 Timestamp Reply
•17 Address Mask Request
•18 Address Mask Reply
•30 Traceroute

17. ICMPv6 Error messages
•Type Value: 1
•Message Name : Destination
Unreachable
•Summary of Message Type:
–Indicates that a datagram could not be
delivered to its destination. Code value
provides more information on the nature of
the error.

18. ICMPv6 Error messages
•Type Value: 2
•Message Name : Packet Too Big
•Summary of Message Type:
–Sent when a datagram cannot be
forwarded because it is too big for the
maximum transmission unit (MTU) of the
next hop in the route. This message is
needed in IPv6 and not IPv4 because in
IPv4, routers can fragment oversized
messages, while in IPv6 they cannot.

19. ICMPv6 Error messages
•Type Value: 3
•Message Name : Time Exceeded
•Summary of Message Type:
–Sent when a datagram has been discarded
prior to delivery due to the Hop Limit field
being reduced to zero.

20. ICMPv6 Error messages
•Type Value: 4
•Message Name : Parameter Problem
•Summary of Message Type:
–Indicates a miscellaneous problem
(specified by the Code value) in delivering
a datagram

21. ICMPv6 Informational messages
•128 Echo Request
•129 Echo Reply
•133 Router Solicitation
•134 Router Advertisement
•135 Neighbor Solicitation
•136 Neighbor Advertisement
•137 Redirect
•138 Router Renumbering

22. Error message rules
ICMP error message must not be
generated in response to any of the
following:
•An ICMP Error Message: This prevents loops.
Note, however, that an ICMP error message can
be generated in response to an ICMP
informational message.
•A Broadcast or Multicast Datagram:
•IP Datagram Fragments Except The First
•Datagrams With Non-Unicast Source
Address:

23. ICMP common format