9: Introduction to ICMPv6
Rick Graziani
Cabrillo College
Rick.Graziani@cabrillo.edu
For more information please check out my Cisco Press book and video series:
IPv6 Fundamentals: A Straightforward
Approach to Understanding IPv6
•
By Rick Graziani
•
ISBN-10: 1-58714-313-5
IPv6 Fundamentals LiveLessons: A
Straightforward Approach to Understanding IPv6
•
By Rick Graziani
•
ISBN-10: 1-58720-457-6
©
9.1: ICMPv6 Messages
ICMP (Internet Control Message Protocol)
Router#ping
MyMac$
debug
www.cabrillo.edu
ip packet detail
PING
IP
packet
mundo.cabrillo.edu
debugging is on
(207.62.187.8):
(detailed)
56 data bytes
64 bytes from 207.62.187.8: icmp_seq=0 ttl=51 time=102.066 ms
64 bytesping
Router#
from192.168.0.4
207.62.187.8: icmp_seq=1 ttl=51 time=125.381 ms
64 bytes
Type
escape
from
sequence
207.62.187.8:
to abort.
icmp_seq=2 ttl=51 time=46.202 ms
64 bytes5,
Sending
from
100-byte
207.62.187.8:
ICMP Echos
icmp_seq=3
to 192.168.0.4,
ttl=51 time=69.447
timeout is 2
msseconds: U.U.U
^C
MyMac$
May
27 05:27:27.11: IP: s=10.0.0.1 (local), d=192.168.0.4 (Serial0), len 100, sending
May 27 05:27:27.15:
ICMP type=8, code=0 ! Echo request sent (ping)
May 27 05:27:27.19: IP: s=10.0.0.2 (Serial0), d=10.0.0.1 (Serial0), len 56, rcvd 3
May 27 05:27:27.23:
ICMP type=3, code=1 ! Local router returns: Destination host
unreachable
May 27 05:27:27.27: IP: s=10.0.0.1 (local), d=192.168.0.4 (Serial0), len 100,
• ICMP is one of the main protocols of the Internet (TCP/IP) suite.
• Used to send messages between devices.
©
ICMPv6
Internet Control Message Protocol for IPv6
• ICMPv6 is defined in RFC 4443.
• Similar to ICMPv4, describes two types of
messages:
• Informational
• Error
• ICMPv6 Neighbor Discovery is described in RFC
4861.
• Much more robust than ICMP for IPv4.
• Contains new functionality and improvements.
• More than just “messaging” but “how IPv6
conducts business”.
Next
IPv6 Main
All ICMPv6
messages
Header
Header
58
ICMPv6
Header
Data
©
ICMPv6 Neighbor Discovery – Lesson 10
ICMPv6 Neighbor Discovery defines 5 different packet types:
• Router Solicitation Message
• Router Advertisement Message
Used with dynamic address allocation
• Neighbor Solicitation Message
• Neighbor Advertisement Message
Used with address resolution (IPv4 ARP)
Router-Device
Messaging
Device-Device
Messaging
• Redirect Message
Similar to ICMPv4 redirect message
Router-to-Device messaging
©
ICMPv6 Messages
• ICMPv6 error messages are:
• Destination Unreachable
• Packet Too Big
• Time Exceeded
• Parameter Problem
Similar to IPv4
We will take a brief look at these
• ICMPv6 informational messages used by the ping command:
• Echo Request
Similar to IPv4
• Echo Reply
We will see a packet analysis example
©
ICMPv6 Messages
ICMPv6 informational messages used for Multicast Listener Discovery
(RFC 2710 ):
• Multicast Listener Query
Similar to IGMP for IPv4
• Multicast Listener Report
(Internet Group Message Protocol)
• Multicast Listener Done
Discussed in Lesson 6
ICMPv6 informational messages used by Neighbor Discovery (RFC 4861):
• Router Solicitation Message
New message types (except for
• Router Advertisement Message
Redirect message).
• Neighbor Solicitation Message
Brief overview.
• Neighbor Advertisement Message
Details discussed in various
• Redirect Message
lessons
©
ICMPv6 General Message Format
Next
Header =
58
IPv6 Header
0
8
Type
ICMPv6 Message
16
Code
24
31
Checksum
Message Body
• IPv6 Next Header Value: 58 decimal or 3A hexadecimal
• ICMPv6 General Message Format (similar to ICMP for IPv4)
©
9.2: ICMPv6 Error Messages
ICMPv6 Error Messages
• ICMPv6 error messages are:
• Destination Unreachable
• Packet Too Big
• Time Exceeded
• Parameter Problem
©
Error Message: Destination Unreachable Message
0
8
Type = 1
16
Code
24
Checksum
Unused
As much of invoking packet as possible without the
ICMPv6 packet exceeding the minimum IPv6 MTU.
Code Values
0 - No route to destination
31 1 - Communication with destination
administratively prohibited
2 - Beyond scope of source
address
3 - Address unreachable
4 - Port unreachable
5 - Source address failed
ingress/egress policy
6 - Reject route to destination
• Sent when a packet cannot be delivered to its destination for reasons
other than congestion.
• A router (or a firewall) usually generates these messages.
• Type = 1
• Code values vary, giving more detail.
©
Error Message: Packet Too Big
0
8
Type = 2
16
Code = 0
24
31
Checksum
MTU of the next hop link
As much of invoking packet as possible without the
ICMPv6 packet exceeding the minimum IPv6 MTU.
• Important difference with IPv6…
• IPv4 routers fragment a packet when the MTU (Maximum Transmission Unit) of
the outgoing link is smaller than the size of the packet.
• The destination device is responsible for reassembling the fragmented packets.
• IPv6 routers do not fragment packets (unless it is the source of the packet).
©
IPv4 Fragmentation
• IPv4 fields used for fragmentation and
reassembly.
• IPv6 routers do not perform
fragmentation.
• Any fragmentation needed will be
handled by the source using an
extension header..
IPv4
IPv6
©
IPv4 Fragmentation
PCA
MTU of outgoing link
smaller than packet size
– fragment IPv4 packet.
R1
R2
Link with
smaller MTU
It is my job to
reassemble the packet
fragments.
PCB
R3
Destination
Source
1
2
IPv4 Packet
3
IPv4
Packet
IPv4
IPv4
Packet
Packet
IPv4
Packet
IPv4
Packet
IPv4
Packet
IPv4
Packet
©
IPv6 No Fragmentation
I will use MTU of the
interface.
PCA
Source
MTU = 1500
MTU of outgoing link smaller
than packet size. Drop packet.
Send ICMPv6 Packet Too Big
message, use MTU 1350.
MTU = 1500
R1
MTU = 1500
MTU = 1350
R2
Link with
smaller MTU
Packet received.
No reassembly
required.
PCB
R3
Destination
1
IPv6 Packet – MTU 1500
2
ICMPv6 Packet Too Big
Use MTU 1350
3
IPv6 Packet
MTU 1350
©
Error Message: Time Exceeded
IPv6
0
8
Type = 3
16
Code = 0
24
31
Checksum
Unused
As much of invoking packet as possible without the
ICMPv6 packet exceeding the minimum IPv6 MTU.
• If a router receives a packet with a Hop Limit of zero, or if a router decrements a
packet's Hop Limit to zero, it MUST:
• Discard the packet
• Send an ICMPv6 Time Exceeded message (Type = 3, Code 0) to the source
of the packet.
• This indicates either a routing loop or too small an initial Hop Limit value.
©
Error Message: Time Exceeded
MyMac$ traceroute6 2001:418:142a:295::90
traceroute6 to 2001:418:142a:295::90 (2001:418:142a:295::90) from
2601:9:6801:85:b953:c971:e56d:1945, 64 hops max, 12 byte packets
1 2601:9:6801:85:cad7:19ff:fe9b:6676 6.306 ms 6.949 ms 9.992 ms
2 2001:558:6045:df::1 29.933 ms 37.620 ms 33.264 ms
3 te-5-4-ur02.scotts.ca.sfba.comcast.net 20.449 ms 23.846 ms 19.910
ms
4 te-1-0-0-10-ar01.oakland.ca.sfba.comcast.net 29.915 ms * *
5 be-90-ar01.sfsutro.ca.sfba.comcast.net 28.884 ms 28.019 ms 19.928
ms
6 he-1-5-0-0-cr01.sanjose.ca.ibone.comcast.net 39.964 ms 28.103 ms
29.734 ms
7 he-0-11-0-0-pe03.11greatoaks.ca.ibone.comcast.net 30.242 ms 26.888
ms 30.151 ms
8 ae-13.r02.snjsca04.us.bb.gin.ntt.net 29.775 ms 27.176 ms 20.832 ms
9 ae-3.r01.snjsca04.us.bb.gin.ntt.net 30.241 ms 28.280 ms 30.185 ms
10 2001:418:1c01:1::80f1:5938 23.455 ms 28.021 ms 26.063 ms
MyMac$
• Windows uses tracert (IPv4 and IPv6) or tracert -6 (IPv6 only)
©
Error Message: Parameter Problem
Code
0
8
Type = 4
16
24
Code
31
0
Erroneous header field
encountered
1
Unrecognized Next Header
type encountered
2
Unrecognized IPv6 option
encountered
Checksum
Pointer
As much of invoking packet as possible without the
ICMPv6 packet exceeding the minimum IPv6 MTU.
Extension Header Name
?
IPv6 Main
Header
Next
Header
138
Extension
Header
Next
Header
6
TCP
Header
Data
• Type 4
• Generated when a receiving device finds a problem with a field in the main IPv6
header such as the Next Header field – packet is discarded.
©
9.3: ICMPv6 Informational Messages:
Echo Request and Echo Reply
ICMPv6 Echo Request and Echo Reply
Type 128 = Echo Request
Type 129 = Echo Reply
0
8
Type = 128/129
16
Code = 0
24
31
Checksum
Sequence Number
Identifier
Data
Ping PCB
ICMPv6 Echo Request
PCA
PCB
ICMPv6 Echo Reply
• Similar to IPv4 Echo Request and Echo Reply messages are used by the ping
utility.
©
Ping Command
PCA
2001:DB8:CAFE:1::/64
G0/0
2001:DB8:CAFE:1::100
FE80::50A5:8A35:A5bb:66E1
R1
2001:DB8:CAFE:1::1
FE80::1
PCA> ping 2001:db8:cafe:1::1
Pinging 2001:db8:cafe:1::1 from 2001:db8:cafe:1::100 with 32 bytes of data:
Reply
Reply
Reply
Reply
from
from
from
from
2001:db8:cafe:1::1:
2001:db8:cafe:1::1:
2001:db8:cafe:1::1:
2001:db8:cafe:1::1:
time=1ms
time=1ms
time=1ms
time=1ms
<rest of output omitted>
PCA>
©
ICMPv6 Echo Request to GUA
Internet Protocol Version 6
0110 .... = Version: 6
<output omitted>
Payload length: 40
Next header: ICMPv6 (0x3a)
Hop limit: 128
Source: 2001:db8:cafe:1::100
Destination: 2001:db8:cafe:1::1
Internet Control Message Protocol v6
Type: 128 (Echo (ping) request)
Code: 0 (Should always be zero)
Checksum: 0x8f38 [correct]
ID: 0x0001
Sequence: 0
IPv6 Header
Data (32 bytes)
ICMPv6 Echo Request
Next
Header =
58
ICMPv6 Message
©
ICMPv6 Echo Reply from GUA
Internet Protocol Version 6
0110 .... = Version: 6
<output omitted>
Payload length: 40
Next header: ICMPv6 (0x3a)
Hop limit: 64
Source: 2001:db8:cafe:1::1
Destination: 2001:db8:cafe:1::100
ICMPv6 Echo Reply
Internet Control Message Protocol v6
Type: 129 (Echo (ping) reply)
Code: 0 (Should always be zero)
Checksum: 0x8e38 [correct]
ID: 0x0001
Sequence: 0
Data (32 bytes)
©
Ping Command
PCA
2001:DB8:CAFE:1::/64
G0/0
2001:DB8:CAFE:1::100
FE80::50A5:8A35:A5bb:66E1
R1
2001:DB8:CAFE:1::1
FE80::1
R1# ping fe80::50a5:8a35:a5bb:66e1
Output Interface: gig 0/0
% Invalid interface. Use full interface name without spaces (e.g. Serial0/1)
Output Interface: gigabitethernet0/0
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to FE80::50A5:8A35:A5BB:66E1, timeout is 2
seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms
R1#
©
ICMPv6 Echo Request to Link-Local Address
Internet Protocol Version 6
0110 .... = Version: 6
<output omitted>
Payload length: 60
Next header: ICMPv6 (0x3a)
Hop limit: 64
Source: fe80::1
Destination: fe80::50a5:8a35:a5bb:66e1
ICMPv6 Echo Request
Source and destination
link-local addresses.
Internet Control Message Protocol v6
Type: 128 (Echo (ping) request)
Code: 0 (Should always be zero)
Checksum: 0x0444 [correct]
ID: 0x0a24
Sequence: 0
Data (52 bytes)
©
ICMPv6 Echo Reply from Link-Local Address
Internet Protocol Version 6
0110 .... = Version: 6
<output omitted>
Payload length: 60
Next header: ICMPv6 (0x3a)
Hop limit: 64
Source: fe80::50a5:8a35:a5bb:66e1
Destination: fe80::1
ICMPv6 Echo Reply
Source and destination
link-local addresses.
Internet Control Message Protocol v6
Type: 129 (Echo (ping) reply)
Code: 0 (Should always be zero)
Checksum: 0x0344 [correct]
ID: 0x0a24
Sequence: 0
Data (52 bytes)
©
ICMPv6 Neighbor Discovery
ICMPv6 Neighbor Discovery defines 5 different packet types:
• Router Solicitation Message
• Router Advertisement Message
Used with dynamic address allocation
• Neighbor Solicitation Message
• Neighbor Advertisement Message
Used with address resolution (IPv4 ARP)
Router-Device
Messaging
Device-Device
Messaging
• Redirect Message
Similar to ICMPv4 redirect message
Router-to-Device messaging
©
For more information please check out my Cisco Press book and video series:
IPv6 Fundamentals: A Straightforward
Approach to Understanding IPv6
•
By Rick Graziani
•
ISBN-10: 1-58714-313-5
IPv6 Fundamentals LiveLessons: A
Straightforward Approach to Understanding IPv6
•
By Rick Graziani
•
ISBN-10: 1-58720-457-6
©
9: Introduction to ICMPv6
Rick Graziani
Cabrillo College
Rick.Graziani@cabrillo.edu