10: ICMPv6 Neighbor Discovery Rick Graziani Cabrillo College [email protected]

10: ICMPv6 Neighbor Discovery

Rick GrazianiCabrillo College

[email protected]

©

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

10.1: Introducing ICMPv6 Neighbor Discovery

©

ICMPv6 Neighbor Discover Protocol

• Router Solicitation Message• Router Advertisement Message

Used with dynamic address allocation

• Neighbor Solicitation Message• Neighbor Advertisement Message

Used with address resolution (IPv4 ARP)

• Redirect Message Similar to ICMPv4 redirect message Router-to-Device messaging

Router-Device Messaging

Device-Device Messaging

ICMPv6 Neighbor Discovery defines 5 different packet types:

See these processes with:R1# debug ipv6 nd

©

ICMPv6 Redirect

• Similar functionality as ICMPv4.• Like IPv4, a router informs an originating host of the IP address of a router that

is on the local link and is closer to the destination. • Unlike IPv4, a router informs an originating host that the destination host (on a

different prefix/network) is on the same link as itself.

Network X

PCA PCB

R1 R2

Destination:Network X Host

Destination:PCB

IPv6 Network A IPv6

Network B

10.2: Router Solicitation and Router Advertisement Messages

©

Dynamic Address Allocation in IPv4DHCPv4 Server

1

2

I need IPv4 addressing information.

Here is everything you need.

©

Dynamic Address Allocation in IPv6

DHCPv6 Server

ICMPv6 Router Advertisement

ICMPv6 Router Solicitation

To all IPv6 routers: I need IPv6 address

information.

To all IPv6 devices:Let me tell you how

to do this … 1. SLAAC

2. SLAAC with Stateless DHCPv6

3. Stateful DHCPv6

SLAAC (Stateless Address Autoconfiguration)

I might not be needed.Router(config)# ipv6 unicast-routing

©

RA Message Options

DHCPv6 Server

ICMPv6 Router AdvertisementOption 1, 2, or 3

Option Other Configuration (“O”) Flag

Managed Configuration (“M”) Flag

Option 1: SLAAC – No DHCPv6 (Default on Cisco routers)

0 0

Option 2: SLAAC + Stateless DHCPv6 for DNS address

1 0

Option 3: All addressing except default gateway use DHCPv6

0 1

Configuring Flags discussed in Lesson 8.

©

Option 3 and the “A” Flag

Option Managed Configuration (“M”) Flag

Address Autoconfiguration (“A”) Flag

Prefix in RA can be used for SLAAC


1 1 (default) Yes


1 0 No

ICMPv6 RAM Flag = 1A Flag = 1

G 0/1

DHCPv6

DHCPv6 Server

As a Windows host I will still use the RA prefix to create

temporary (SLAAC) addresses)

0

The autonomous address configuration (A) flag tells hosts that they can create an address for themselves by combining the prefix in the RA with an interface identifier.

Configuring Flags discussed in Lesson 8.

©

To: FF02::1 (All-IPv6 devices)

From: FE80::1 (Link-local address)

ICMPv6 Router Advertisement

RA

2

Link-local: FE80::50A5:8A35:A5BB:66E1MAC: 00-21-9b-d9-c6-44

2001:DB8:CAFE:1::/64

1

Router Solicitation / Router Advertisement

To: FF02::2 (All-IPv6 Routers)

From: FE80::50A5:8A35:A5BB:66E1

ICMPv6 Router SolicitationRS

Router Solicitation• Sent when device needs IPv6

addressing information.Router Advertisement• Sent every 200 seconds or in

response to RS

Link-local: FE80::1MAC: 00-03-6b-e9-d4-80R1

PC1

©

Analyzing the Router Solicitation Message

©

Ethernet II, Src: 00:21:9b:d9:c6:44, Dst: 33:33:00:00:00:02

Internet Protocol Version 6 0110 .... = Version: 6 [Traffic class and Flowlabel not shown] Payload length: 16 Next header: ICMPv6 (0x3a) Hop limit: 255 Source: fe80::50a5:8a35:a5bb:66e1 Destination: ff02::2

Internet Control Message Protocol v6 Type: 133 (Router solicitation) Code: 0 Checksum: 0x3277 [correct] ICMPv6 Option (Source link-layer address) Type: Source link-layer address (1) Length: 8 Link-layer address: 00:21:9b:d9:c6:44

Link-local address of PC1

All-IPv6-routers multicast address

Router Solicitation message

MAC address of PC1 but RAis sent as all-IPv6-host multicast

Next header is an ICMPv6 header

Ethernet multicast MAC address – Maps to “all IPv6 routers”

Router Solicitation Message

©

Analyzing the Router Advertisement Message

©

R1(config)# ipv6 unicast-routing

R1# show ipv6 interface gigabitethernet 0/0GigabitEthernet0/0 is up, line protocol is up IPv6 is enabled, link-local address is FE80::1 Global unicast address(es): 2001:DB8:CAFE:1::1, subnet is 2001:DB8:CAFE:1::/64 Joined group address(es): FF02::1 FF02::2 FF02::1:FF00:1 MTU is 1500 bytes <output omitted for brevity> ND advertised retransmit interval is 0 milliseconds ND router advertisements are sent every 200 seconds ND router advertisements live for 1800 seconds Hosts use stateless autoconfig for addresses.

All-routers multicast group

M & O flags = 0

An IPv6 Router

©

Ethernet II, Src: 00:03:6b:e9:d4:80, Dst: 33:33:00:00:00:01

Internet Protocol Version 6 0110 .... = Version: 6 .... 1110 0000 .... .... .... .... .... = Traffic class: 0x000000e0 .... .... .... 0000 0000 0000 0000 0000 = Flowlabel: 0x00000000 Payload length: 64 Next header: ICMPv6 (0x3a) Hop limit: 255 Source: fe80::1 Destination: ff02::1

Link-local address of R1. Added to hosts’ Default Router List and is the address they will use as their default gateway.

All-IPv6 devices multicast

Next Header is an ICMPv6 header

Ethernet multicast MAC address – Maps to “All-IPv6 devices”

Analyzing the Router Advertisement Message

Continued next slide

©

Internet Control Message Protocol v6 Type: 134 (Router advertisement) Code: 0 Cur hop limit: 64 Flags: 0x00 ICMPv6 Option (Source link-layer address) Type: Source link-layer address (1) Length: 8 Link-layer address: 00:03:6b:e9:d4:80 ICMPv6 Option (MTU) Type: MTU (5) Length: 8 MTU: 1500 ICMPv6 Option (Prefix information) Type: Prefix information (3) Length: 32 Prefix Length: 64 Prefix: 2001:db8:cafe:1::

Recommended Hop Limit value for hosts

M and O flags indicate that no information is available via DHCPv6

Router R1’s MAC address

MTU of the link.

Prefix-length (/64) to be used for autoconfiguration.

Prefix of this network to be used for autoconfiguration

Router Advertisement

Router Advertisement Message

10.3: Neighbor Solicitation and Neighbor Advertisement Messages

©

Ethernet ARP Request/Reply

ICMPv6: Neighbor Solicitation/Advertisement

IPv4: ARP over Ethernet

PC1PC2ARP Request

Neighbor Advertisement

1

2Neighbor

Solicitation

1

ARP Reply

2

Know IPv4, what

is the MAC?

My IPv4! Here is the

MAC?

Know IPv6, what

is the MAC?

My IPv6! Here is the

MAC?

ARP Request: Broadcast

NS: Multicast NS: Solicited Node Multicast

Ethernet IPv6 Header

IPv6: ICMPv6 over IPv6 over Ethernet

Address Resolution: IPv4 and IPv6

ARP Cache

Neighbor Cache

©

PC1PC2


4Neighbor

Solicitation

1

Neighbor Solicitation and Neighbor Advertisement

2001:DB8:CAFE:1::100/64

MAC Address00-21-9B-D9-C6-44

Neighbor Cache<empty until step 5>

2001:DB8:CAFE:1::200/64FF02::1:FF00:200 (Solicited Node Multicast)

MAC Address00-1B-24-04-A2-1E

ICMPv6: Neighbor Solicitation/Advertisement

NS: Multicast NS: Solicited Node Multicast

Ethernet IPv6 Header

PC1> ping 2001:DB8:CAFE:1::200

2 53

NA: Unicast NA: Unicast

©

Neighbor Solicitation

PC1PC2



Neighbor CacheMAC Address

00-1B-24-04-A2-1E

2001:DB8:CAFE:1::100/642001:DB8:CAFE:1::200/64FF02::1:FF00:200 (Solicited Node Multicast)

I know the IPv6, but

what is the MAC?

©

Ethernet II, Src: 00:21:9b:d9:c6:44, Dst: 33:33:ff:00:02:00

Internet Protocol Version 6 0110 .... = Version: 6 .... 0000 0000 .... .... .... .... .... = Traffic class: 0x00000000 .... .... .... 0000 0000 0000 0000 0000 = Flowlabel: 0x00000000 Payload length: 32 Next header: ICMPv6 (0x3a) Hop limit: 255 Source: 2001:db8:cafe:1::100 Destination: ff02::1:ff00:200

Internet Control Message Protocol v6 Type: 135 (Neighbor solicitation) Code: 0 Checksum: 0xbbab [correct] Reserved: 0 (Should always be zero) Target: 2001:db8:cafe:1::200 ICMPv6 Option (Source link-layer address) Type: Source link-layer address (1) Length: 8 Link-layer address: 00:21:9b:d9:c6:44

Global unicast address of PC1Solicited-node multicast address of PC2

Neighbor Solicitation message

Target IPv6 address, needing MAC address (if two devices have the same solicited node address, this resolves the issue)


MAC address of the sender, PC1

Mapped multicast address for PC2

PC1NS

©


PC1PC2



Neighbor Cache

MAC Address00-1B-24-04-A2-1E

2001:DB8:CAFE:1::100/642001:DB8:CAFE:1::200/64FF02::1:FF00:200 (Solicited Node Multicast)

It’s my IPv6 and here is my MAC?

©

Ethernet II, Src: 00:1b:24:04:a2:1e, Dst: 00:21:9b:d9:c6:44

Internet Protocol Version 6 0110 .... = Version: 6 .... 0000 0000 .... .... .... .... .... = Traffic class: 0x00000000 .... .... .... 0000 0000 0000 0000 0000 = Flowlabel: 0x00000000 Payload length: 32 Next header: ICMPv6 (0x3a) Hop limit: 255 Source: 2001:db8:cafe:1::200 Destination: 2001:db8:cafe:1::100

Internet Control Message Protocol v6 Type: 136 (Neighbor advertisement) Code: 0 Checksum: 0x1b4d [correct] Flags: 0x60000000 Target: 2001:db8:cafe:1::200 ICMPv6 Option (Target link-layer address) Type: Target link-layer address (2) Length: 8 Link-layer address: 00:1b:24:04:a2:1e


Unicast MAC address of PC1

Global unicast address of PC2

Global unicast address of PC1

Neighbor Advertisement message

MAC address of the sender, PC2

IPv6 address of the sender, PC2

PC2NA

©

ICMPv6 Duplicate Address Detection (DAD)

• Duplicate Address Detection (DAD) is used to guarantee that an IPv6 unicast address is unique on the link.

• A device will send a Neighbor Solicitation for its own unicast address (static or dynamic).

• After a period of time, if a NA is not received, then the address is deemed unique.

• Once required, RFC was updated to where it is only recommended - /64 Interface ID makes duplicates unlikely!

PC2

Hopefully noNeighbor Advertisement


Global Unicast - 2001:DB8:CAFE:1::200Link-local - FE80::1111:2222:3333:4444

See the process with:R1# debug ipv6 nd

10.4: Neighbor Cache

©

Neighbor Cache

PC1Neighbor Cache

IPv6 Address MAC Address2001:DB8:ACAD:1::10 0021.9bd9.c644 IPv6 - 2001:DB8:ACAD:1::10

MAC - 0021.9bd9.c644

Neighbor AdvertisementNeighbor Solicitation

?

• Neighbor Cache – Maps IPv6 addresses with Ethernet MAC addresses• Similar to ARP Cache for IPv4

• 5 States (2 noticeable and 3 transitory): • Reachable: Packets have recently been received providing confirmation that this

device is reachable.• Stale: A certain time period has elapsed since a packet has been received from

this address.• Transitory States: INCOMPLETE, DELAY, PROBE

©

R1# show ipv6 neighborsIPv6 Address Age Link-layer Addr State InterfaceFE80::50A5:8A35:A5BB:66E1 16 0021.9bd9.c644 STALE Fa0/02001:DB8:AAAA:1::100 16 0021.9bd9.c644 STALE Fa0/0

R1# ping 2001:db8:aaaa:1::100

Type escape sequence to abort.Sending 5, 100-byte ICMP Echos to 2001:DB8:AAAA:1::100, timeout is 2 seconds:!!!!!Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/1 msR1# show ipv6 neighborsIPv6 Address Age Link-layer Addr State InterfaceFE80::50A5:8A35:A5BB:66E1 16 0021.9bd9.c644 STALE Fa0/02001:DB8:AAAA:1::100 0 0021.9bd9.c644 REACH Fa0/0

R1#

Neighbor Cache

©

No Entry Exists Incomplete

Reachable

Stale – no action required(Requires resolution again)

Delay(Resolution pending)

Probe(Reresolution in progress)

Neighbor Solicitation (NS) sent

NA receivedReachable Time exceeded (default 30 sec) OrUnsolicited NA received

Packet sent

Packet returned (TCP increasing ACK)

5 sec

NS sent andNA received

3 NS sent with no NA returned

3 NS sent with no NA returned

Neighbor Cache (“ARP Cache”)

Neighbor Cache FSM

See the process with:R1# debug ipv6 nd

©

R1# debug ipv6 nd ICMP Neighbor Discovery events debugging is onR1# ping 2001:db8:aaaa:1::100Type escape sequence to abort.Sending 5, 100-byte ICMP Echos to 2001:DB8:AAAA:1::100, timeout is 2 seconds:!!!!!Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms*Oct 16 01:41:51.575: ICMPv6-ND: (GigabitEthernet0/1,2001:DB8:AAAA:1::100) Resolution request*Oct 16 01:41:51.575: ICMPv6-ND: Created ND Entry Chunk pool*Oct 16 01:41:51.575: ICMPv6-ND: (GigabitEthernet0/1,2001:DB8:AAAA:1::100) DELETE -> INCMP*Oct 16 01:41:51.575: ICMPv6-ND: (GigabitEthernet0/1,2001:DB8:AAAA:1::100) Sending NS*Oct 16 01:41:51.575: ICMPv6-ND: (GigabitEthernet0/1,2001:DB8:AAAA:1::100) Queued data for

resolution*Oct 16 01:41:51.579: ICMPv6-ND: (GigabitEthernet0/1,2001:DB8:AAAA:1::100) Received NA from

2001:DB8:AAAA:1::100*Oct 16 01:41:51.579: ICMPv6-ND: Validating ND packet options: valid*Oct 16 01:41:51.579: ICMPv6-ND: (GigabitEthernet0/1,2001:DB8:AAAA:1::100) LLA c471.fe7d.9c29*Oct 16 01:41:51.579: ICMPv6-ND: (GigabitEthernet0/1,2001:DB8:AAAA:1::100) INCMP -> REACH*Oct 16 01:42:21.639: ICMPv6-ND: (GigabitEthernet0/1,2001:DB8:AAAA:1::100) REACH -> STALER1#

Neighbor Cache

©

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

10: ICMPv6 Neighbor Discovery

Rick GrazianiCabrillo College

[email protected]

Documents

10: ICMPv6 Neighbor Discovery Rick Graziani Cabrillo College [email protected]