1. Help! I need to Understand IPv6 Addresses
Rick Graziani
Cabrillo College

2. STEAL MY STUFF! www.cabrillo.edu/~rgraziani/ipv6.html Shameless plug:
Username = cisco
Password = perlman
Shameless plug:
IPv6 Fundamentals: A Straightforward Approach to Understanding IPv6
By Rick Graziani
ISBN-10:
IPv6 Fundamentals LiveLessons: A Straightforward Approach to Understanding IPv6
By Rick Graziani
ISBN-10:

3. Running Out of IPv4
The regions with the largest populations have the lowest percentages of people connected to the Internet
Graphic from Internet World Stats,

4. (One /8 left)
The ARIN IPv4 Countdown Plan is in Phase 4, and we will continue working in Phase 4 as we move toward full depletion of ARIN's available IPv4 inventory.

5. CENIC customers may be allocated space no larger than a /27 (32 usable addresses).
In all cases, utilization of 85% or greater must be demonstrated before additional space will be allocated.

6. Representing an IPv6 Address

7. The Beauty of Hexadecimal: 4 bits = 1 hex digit
Binary
8421
0000
0001
0010
0011
0100
0101
0110
0111
Binary
8421
1000
1001
1010
1011
1100
1101
1110
1111
Dec 1 2 3 4 5 6 7
Hex 1 2 3 4 5 6 7
Dec 8 9 10 11 12 13 14 15
Hex 8 9 A B C D E F
Any combination of 4 bits (16 possibilities) can be represented by a single hexadecimal digit

8. IPv6 Address Notation 2001:0DB8:AAAA:1111:0000:0000:0000:0100
16 bits 1
16 bits 2
16 bits 3
16 bits 4
16 bits 5
16 bits 6
16 bits 7
16 bits 8
IPv6 addresses are 128-bit addresses represented in:
Hexadecimal: 1 hex digit = 4 bits
Eight 16-bit segments or “hextets” (not a formal term) between 0000 and FFFF
Separated by colons
Reading and subnetting IPv6 is easier than IPv4…. Really!
[RFC4291] does not mention any preference of uppercase or lowercase.
The RFC 5952 recommendation that SHOULD be followed is that characters be represented in lower text by systems when generating an
address to be represented as text, but all implementations MUST accept and be able to handle any legitimate [RFC4291] format.

9. Number of IPv6 Addresses
Number name
Scientific Notation
Number of zeros
1 Thousand
103
1,000
1 Million
106
1,000,000
1 Billion
109
1,000,000,000
1 Trillion
1012
1,000,000,000,000
1 Quadrillion
1015
1,000,000,000,000,000
1 Quintillion
1018
1,000,000,000,000,000,000
1 Sextillion
1021
1,000,000,000,000,000,000,000
1 Septillion
1024
1,000,000,000,000,000,000,000,000
1 Octillion
1027
1,000,000,000,000,000,000,000,000,000
1 Nonillion
1030
1,000,000,000,000,000,000,000,000,000,000
1 Decillion
1033
1,000,000,000,000,000,000,000,000,000,000,000
1 Undecillion
1036
1,000,000,000,000,000,000,000,000,000,000,000,000
IPv4
4.3 billion
IPv4 addresses:
4.3 billion
IPv6 addresses:
340 undecillion
IPv6
340 undecillion
340,282,366,920,938,463,463,374,607,431,768,211,456

10. Two Rules for Compressing IPv6 Addresses Rule 1: Omitting Leading 0s
Two rules for reducing the size of written IPv6 addresses.
First rule: Leading zeroes in any 16-bit segment do not have to be written.
2001 : 0DB8 : 0001 : 1000 : 0000 : 0000 : 0ef0 : bc00
2001 : DB8 : 1 : 1000 : 0 : 0 : ef0 : bc00
2001 : 0DB8 : 010d : 000a : 00dd : c000 : e000 : 0001
2001 : DB8 : 10d : a : dd : c000 : e000 : 1
2001 : 0DB8 : 0000 : 0000 : 0000 : 0000 : 0000 : 0500
2001 : DB8 : 0 : 0 : 0 : 0 : 0 : 500
Only leading 0s, not trailing 0s.
Otherwise we wouldn’t know which 0s were omitted – leading 0s, trailing 0s, or both.
By the way, I’m using spaces between the hextets only for readability.

11. Two Rules for Compressing IPv6 Addresses Rule 1: Omitting Leading 0s
Only leading 0s can be excluded, trailing 0s must be included.
Or leads to ambiguity…
2001 : 0DB8 : ab : 1234 : 5678: 9abcd: ef12: 3456
2001 : 0DB8 : 00ab : 1234 : 5678: 9abcd: ef12: 3456
2001 : 0DB8 : ab00 : 1234 : 5678: 9abcd: ef12: 3456
2001 : 0DB8 : 0ab0 : 1234 : 5678: 9abcd: ef12: 3456 ?
Only leading 0s, not trailing 0s.
Otherwise we wouldn’t know which 0s were omitted – leading 0s, trailing 0s, or both.
By the way, I’m using spaces between the hextets only for readability.

12. Two Rules for Compressing IPv6 Addresses
Rule 2: Double Colon ::
The second rule can reduce this address even further:
Second rule: Any single, contiguous string of one or more 16-bit segments consisting of all zeroes can be represented with a double colon (::).
2001 : 0DB8 : 1000 : 0000 : 0000 : 0000 : 0000 : 0001
2001 : DB8 : 1000 : : 1
2001:DB8:1000::1
First rule
Second rule
First rule

13. Rule 2: Double Colon :: Choices
Only a single contiguous string of all-zero segments can be represented with a double colon.
Although the rule states that both of these are correct…
2001 : DB8 : 0000 : 0000 : 1234 : 0000 : 0000 : 5678
2001 : DB :: 1234 : 0 : 0 : 5678
2001 : DB8 : 0 : 0 : :: 5678
RFC 5952 or
… RFC 5952 states that the longest string of zeroes must be replaced with the :: and if they are equal then the first string of 0’s should use the :: representation.
RFC 5952 does state that the longest string of zeroes must be replaced w/ the :: and if they are equal then the first string of 0’s should use the :: representation
RFC 5952 A Recommendation for IPv6 Address Text Representation provides clarity on how addresses should be represented
Maximum reduction of the address is known as the “compressed” format.

14. Rule 2: Double Colon :: Only Once
Using the double colon more than once in an IPv6 address can create ambiguity because of the ambiguity in the number of 0s.
2001:DB8::1234::5678
2001:DB8:0000:0000:0000:1234:0000:5678
2001:DB8:0000:0000:1234:0000:0000:5678
2001:DB8:0000:1234:0000:0000:0000:5678

15. The IPv6 Prefix Length

16. IPv4: Subnet Mask and Prefix Length
Prefix Subnet
Binary Mask Length Mask / / / / / / / / / / / / / / / / / / / / / / / / /
The prefix length is the number of bits set in the subnet mask; for instance, if the subnet mask is , there are 24 1’s in the binary version of the subnet mask, so the prefix length is 24 bits.

17. Terminology 2001:DB8:CAFE:1::0001/64 Prefix Interface ID Terminology:
Prefix equivalent to the network address of an IPv4 address
Prefix length equivalent to subnet mask in IPv4
Interface ID equivalent to host portion of an IPv4 address

18. IPv6 Prefix Length 2001:0DB8:0000:0000:0000:0000:0000:0001 /32 /48 /52
IPv6 prefixes are always identified by prefix length.
Written immediately following the IPv6 address, usually no space.
The prefix length does not have to fall on a nibble (4-bit) boundary…. But make your life easier! (See hidden slide)
Hex digit = 4 bits :Hextet: = 16 bits
Prefix
Interface ID
2001:0DB8:0000:0000:0000:0000:0000:0001
Prefix length
/32
/48
/52
/56
/60
/64
A nibble is 4 bits

19. IPv6 Prefix Length Prefixes (network/subnet address): 2001:DB8::/32
2001:DB8:CAFE::/48
2001:DB8:CAFE:1::/64
2001:DB8:CAFE:1234::/64
Just count hextets!
/32 = 2 hextets
/48 = 3 hextets
/64 = 4 hextets (user subnets, LANs)
IPv6 devices (hosts, etc.):
2001:DB8:CAFE::1/48
2001:DB8:CAFE::99:2/48
2001:DB8:CAFE:1::100/64
2001:DB8:CAFE:1:AAAA:BBBB:CCCC:DDDD/64
You will become more familiar with these addresses – other lessons and by using IPv6

20. Overview of IPv6 Addresses Address Types

21. IPv6 Address Types…. Road Map
IPv6 Addresses
Lesson 6
Unicast
Multicast
Anycast
Assigned
Solicited Node
FF00::/8
FF02::1:FF00:0000/104
Lesson 4
Lesson 5
Global Unicast
Link-Local
Loopback
Unspecified
Unique Local
Embedded IPv4
2000::/3
FE80::/10
::1/128
::/128
FC00::/7
::/80
RFC Default Address Selection for IPv6 (includes IPv4)
Much more later other lessons, and used throughout this video series
IPv6 does not have a broadcast address however, there is an all-IPv6-devices multicast. We will explain how that is different in Lesson 6
IPv6 does not have a “broadcast” address.

22. IPv6 Source and Destination Addresses
IPv6 Source – Always a unicast
IPv6 Destination – Unicast, multicast or anycast.
Unicast includes Global Unicast or Link-Local Unicast.
IPv4
IPv6
Much more in later lessons

23. Global Unicast Address
IPv6 Internet
Global Unicast Address (GUA)
2000::/3 (First hextet: 2000::/3 to 3FFF::/3)
Globally unique and routable
Similar to public IPv4 addresses
2001:DB8::/32 - RFC 2839 and RFC 6890 reserves this range of addresses for documentation
These are the addresses we will be referring to the most.
RFC 6890 lists other special use blocks for both IPv4 and IPv6 blocks.

24. Global Unicast Address Range
Global Routing Prefix
Subnet ID
Interface ID
001
Range: 2000:
3FFF: : :
First hextet
Global Unicast Address (GUA)
2000::/3
First hextet: 2000::/3 to 3FFF::/3
1/8th of IPv6 address space
IANA’s allocation of IPv6 address space in 1/8th sections

25. Parts of a Global Unicast Address
IPv4 Unicast Address /?
Network portion
Subnet portion
Host portion
32 bits
IPv6 Global Unicast Address
/48
/64
16-bit Subnet ID
Global Routing Prefix
Interface ID
128 bits
64-bit Interface ID = 18 quintillion (18,446,744,073,709,551,616) devices/subnet
16-bit Subnet ID (initially recommended) = 65,536 subnets
/48 global routing prefix could be more or less depending on what you service provider gives you – we will talk about this in a moment
Most orgs that go to ARIN are more likely to get a /40 w/ the ARIN assignment policy based on the number of sites. So you actually end w/ a more variable length “subnet” range that you can use. The /48 boundary was initially recommended by the first IPv6 standards but it is changing.

26. /64 Global Unicast Address and the 3-1-4 Rule
/48
/64
16 bits
16 bits
16 bits
16 bits
16 bits
16 bits
16 bits
16 bits
Global Routing Prefix
Subnet ID
Interface ID 3 1 4
2001 : 0DB8 : CAFE : 0001 : 0000 : 0000 : 0000 : 0100
3 + 1 = 4 (/64) : 4
2001:0DB8:CAFE:0001:0000:0000:0000:0100/64
2001:DB8:CAFE:1::100/64
3-1-4 when using a /48 (common but a moving target)

27. Global Routing Prefix determines number of /64 subnets *
Subnet ID
18 quintillion hosts per subnet
2001:DB8:0000:0000:0000:0000:0000:0000
From your ISP or ARIN
/32 UCSC from ARIN
/48 Cabrillo from CENIC
64-bit Interface ID
/60 (4-bit Subnet ID) = 16 subnets
/56 (8-bit Subnet ID) = 256 subnets
/52 (12-bit Subnet ID) = 4,096 subnets
IPv6 lets us create a well organized and easy to manage addressing plan without having to try and conserve addresses.
(Many sites will get this prefix length)
/48 = (16-bit Subnet ID) 65,536 subnets
/44 = (20-bit Subnet ID) 1,048,576 subnets
/40 (24-bit Subnet ID) = 16,777,216 subnets
/36 (28-bit Subnet ID) = 268,435,456 subnets
/32 (32-bit Subnet ID) = 4,294,967,296 subnets
You use /64 subnets.
As many IPv6 subnets as there are IPv4 addresses!

28. Subnetting IPv6 in Two Minutes or Less
Can you count in hex?
Just increment by 1 in Hexadecimal:
2001:0DB8:CAFE:0000::/64
2001:0DB8:CAFE:0001::/64
2001:0DB8:CAFE:0002::/64 ...
2001:0DB8:CAFE:0009::/64
2001:0DB8:CAFE:000A::/64
Valid abbreviation is to remove the leading 0s:
2001:DB8:CAFE:1::/64
/48 from ISP
Creating /64 subnets
3-1-4 Rule

29. Manual Configuration of IPv6 Addresses Allocation (SLAAC and DHCPv6)

30. Static GUA Configuration
2001:DB8:CAFE:1::/64
:100 A
G0/0 :1
2001:DB8:CAFE:3::/64 :1
S0/0/0 :1
G0/1 R1
:100 B
2001:DB8:CAFE:2::/64
R1(config)#interface gigabitethernet 0/0
R1(config-if)#ipv6 address 2001:db8:cafe:1::1/64
R1(config-if)#no shutdown
R1(config-if)#exit
No space
Exactly the same as an IPv4 address only different.
No space between IPv6 address and Prefix-length.
IOS commands for IPv6 are very similar to their IPv4 counterpart.
All 0’s and all 1’s are valid IPv6 host IPv6 addresses.

31. Static GUA Configuration
2001:DB8:CAFE:1::/64
:100 A
G0/0 :1
2001:DB8:CAFE:3::/64 :1
S0/0/0 :1
G0/1 R1
:100 B
2001:DB8:CAFE:2::/64
I love the rule and subnetting IPv6!
R1(config)#interface gigabitethernet 0/1
R1(config-if)#ipv6 address 2001:db8:cafe:2::1/64
R1(config-if)#no shutdown
R1(config-if)#exit
R1(config)#interface serial 0/0/0
R1(config-if)#ipv6 address 2001:db8:cafe:3::1/64 
The ipv6 unicast-routing global configuration command is required for forward IPv6 packets – it is not required to configure IPv6 addresses.

32. Verifying Address Using Running Configuration
2001:DB8:CAFE:1::/64
:100 A
G0/0 :1
2001:DB8:CAFE:3::/64 :1
S0/0/0 :1
G0/0 R1
:100 B
2001:DB8:CAFE:2::/64
R1# show running-config
<output omitted for brevity>
interface GigabitEthernet0/0
no ip address
duplex auto
speed auto
ipv6 address 2001:DB8:CAFE:1::1/64 !
IPv4 address
IPv6 address

33. Verifying Unicast Addresses on R1
R1# show ipv6 interface brief
GigabitEthernet0/0 [up/up]
FE80::FE99:47FF:FE75:C3E0
2001:DB8:CAFE:1::1
! <output omitted>
Link-local unicast address
Global unicast address
Link-local and global unicast addresses are displayed.
Link-local address automatically created when (before) the global unicast address is.
Link-local addresses are used for communicating with other devices on the same link (not routable).
We will discuss link-local addresses in Lesson 5.
Link-local address play an important part in IPv6 networking – so be sure you have a good understanding of them.

34. Static GUA Configuration on PC
Same as IPv4 devices:
Servers, printers, routers, etc.
Can also be a link-local unicast address of the router.
So one issue to mention here is that even if a static address is configured on the host, it could possibly pick up a SLAAC address.
In other words configuring a static address does not mean that will be the only global address on the end system. If the router is sending RA’s, the host could get both a static and a SLAAC assigned address.

35. Verifying Unicast Addresses on PC
PCA> ipconfig Windows IP Configuration Ethernet adapter Local Area Connection: Connection-specific DNS Suffix : IPv6 Address : 2001:db8:cafe:1::100 Link-local IPv6 Address : fe80::50a5:8a35:a5bb:66e1 Default Gateway : 2001:db8:cafe:1::1
Link-local addresses are created automatically.
Recent Microsoft operating systems use a random 64-bit Interface ID for link-local address… (coming soon)

36. Verifying IPv6 Connectivity
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 from 2001:db8:cafe:1::1: time=1ms
Ping statistics for 2001:db8:cafe:1::1:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 1ms, Maximum = 1ms, Average = 1ms
PCA>
Don’t be intimidated with IPv6. It’s still all about packets getting from one place to another. If the ping fails, then troubleshoot it like you would IPv4.

37. Dynamic Configuration of IPv6 Addresses Allocation (SLAAC and DHCPv6)

38. Dynamic IPv6 Address Allocation
Global Unicast
Next Presentation!
Manual
Dynamic
Stateless
Stateful
Static
IPv6 unnumbered
SLAAC
DHCPv6
Similar to IPv4 unnumbered
Static + EUI 64
SLAAC + DHCPv6
DHCPv6-PD

39. Dynamic IPv4 Address Allocation
I need IPv4 addressing information from a DHCP server.
DHCP Server
DHCP Client
Here is your IPv4 address, subnet mask, default gateway and DNS server addresses.

40. It Begins with the RA Message
Multicast: To all IPv6 routers, I need IPv6 address information
Router(config)# ipv6 unicast-routing
ICMPv6 Router Advertisement
ICMPv6 Router Solicitation
DHCPv6 Server
Multicast: To all IPv6 devices,
let me tell you how to do this …
I might not even be needed. 
An ICMPv6 Router Advertisement (RA) suggests to all IPv6 devices on the link how it will receive IPv6 Address Information.
Sent periodically by an IPv6 router or…
… when the router receives a Router Solicitation message from a host.
Routers can be configured with IPv6 addresses without being an IPv6 router.

41. Router Advertisement: 3 Options
Option 1 and 2: Stateless Address Autoconfiguration
DHCPv6 Server does not maintain state of addresses
Option 3: Stateful Address Configuration
Address received from DHCPv6 Server
DHCPv6
Router(config)# ipv6 unicast-routing
DHCPv6 Server
Option 1: SLAAC – No DHCPv6 (Default on Cisco routers)
“I’m everything you need (Prefix, Prefix-length, Default Gateway)”
Option 2: SLAAC + Stateless DHCPv6 for DNS address
“Here is my information but you need to get other information such as DNS addresses from a DHCPv6 server.” (DNS can be in RA)
Option 3: All addressing except default gateway – DHCPv6
“I can’t help you. Ask a DHCPv6 server for all your information.” RA
you can send DNS server information in RA’s now. Again it is a two part problem, the routers have to support sending the information and the end systems have to know what to do with it.

42. Purpose and Format of Link-Local Addresses

43. IPv6 Address Types IPv6 Addresses Unicast Multicast Anycast Assigned
Solicited Node
FF00::/8
FF02::1:FF00:0000/104
Global Unicast
Link-Local
Loopback
Unspecified
Unique Local
Embedded IPv4
2000::/3
FE80::/10
::1/128
::/128
FC00::/7
::/80
IPv6 does not have a “broadcast” address.

44. Link-Local Unicast Range
First 10 bits
Remaining 54 bits
xx xxxx
64-bit Interface ID
Range: FE80:
FEBF: : :
First hextet
Link-local Unicast
Link – Network segment
Link-local means, local to that link or network.

45. Link-Local Unicast Address
IPv6 Source – Always a unicast
IPv6 Destination – Unicast, multicast, or anycast.
Unicast, including a link-local address
IPv4
IPv6

46. Link-Local Unicast Address Link-Local Communications
Used to communicate with other devices on the link.
Are NOT routable off the link (network).
Only have to be unique on the link.
Not included in the IPv6 routing table.
An IPv6 device must have at least a link-local address.
Might mention here that link local addresses are intended to provide a stable communications address as global addresses may change over time whereas link local addresses are consistent and constantly available (for the most part)

47. Most Networks Are Already Running IPv6
I’m not running IPv6… or am I?
I can now communicate with you and give you a GUA and be your default gateway using SLAAC.
But I am really a bad guy and I can do a DoS or MITM attack.
PC> ipconfig Windows IP Configuration Ethernet adapter Local Area Connection: Connection-specific DNS Suffix : Link-local IPv6 Address : fe80::50a5:8a35:a5bb:66e1 IPv4 Address : Subnet Mask : Default Gateway :
Even if IPv6 is not deployed, must understand and secure IPv6.
IPv6 is automatically enabled with Windows, MAC and Linux operating systems.
Can communicate with other devices on the link, including the router.
Similar security issues and solutions as IPv4.
Highlight on the second bullet that IPv6 comms can happen even if constructs are in place to prevent such comms (e.g. IPv4 acl) I think the graphic build up gets to it but maybe worth highlighting.
Might also be worth highlighting that even if you don’t intend to deploy IPv6 you still need to secure and provide instrumentation and processes to detect IPv6.
People Icon: Occupations set 5 © Copyright Fredy Sujono

48. An Important Role in IPv6
Routing Protocol Messaging
From: Link-local
To: Multicast
ICMPv6 Router Solicitation
From: Link-local or unspecified address
To: Multicast
ICMPv6 Router Advertisement
From: Link-local
To: Multicast
I will use your link-local as my default gateway,
Used as a source IPv6 address before a device gets one dynamically (SLAAC and DHCPv6).
Router’s link-local address is used by devices as the default gateway.
Routers exchange routing messages.
Router use the link-local address as the next-hop address in the routing table: via link-local address.

49. 5.2: Automatically Created Link-Local Addresses

50. Link-Local Unicast Address
First 10 bits
Remaining 54 bits
xx xxxx
64-bit Interface ID
FE80::Interface ID
Link-local addresses are created
Automatically :
FE80 (usually) – First 10 bits
Interface ID
EUI-64 (Cisco routers)
Random 64 bits (many host operating systems)
Static (manual) configuration – Common practice for routers.

51. Automatic Link-Local Address Using EUI-64
R1# show interface gigabitethernet 0/0
GigabitEthernet0/0 is up, line protocol is up
Hardware is CN Gigabit Ethernet, address is fc c3e0 (bia fc c3e0)
<Output Omitted>
Link-local address: FE80:: 64-bit Interface ID
A 64-bit Interface ID is created with EUI-64 using:
48-bit MAC address
Inserting 16 bits: FF-FE
Flipping the U/L (Universal/Local) bit
EUI-64 can also be used to automatically create Global Unicast Addresses (next presentation)

52. Modified EUI-64 Format (Extended Unique Identifier–64)
OUI (24 bits)
Device Identifier (24 bits) FC 99 47 75 C3 E0
Insert FF-FE FC 99 47 FF FE 75 C3 E0 FC 99 47 FF FE 75 C3 E0
U/L bit flipped FE 99 47 FF FE 75 C3 E0
Insert FFFE gives us a 64 bit Interface ID
IPv6 64-bit interface IDs are on a 64 bit boundary and accommodate IEEE specification for 64 bit MAC addresses
IEEE has chosen FFFE as a reserved value which can only appear in EUI-64 generated from the an EUI-48 MAC address. IEEE's Guidelines for EUI-64 Registration Authority,
Reason for U/L bit flipped can be found in RFC 4291 IP Version 6 Addressing Architecture

53. Verifying the Router’s Link-Local Address
Link-local addresses only have to be unique on the link.
R1# show interface gigabitethernet 0/0
GigabitEthernet0/0 is up, line protocol is up
Hardware is CN Gigabit Ethernet, address is fc c3e0 (bia fc c3e0)
<Output Omitted>
R1#show ipv6 interface brief
GigabitEthernet0/0 [up/up]
FE80::FE99:47FF:FE75:C3E0
2001:DB8:CAFE:1::1
GigabitEthernet0/1 [up/up]
FE80::FE99:47FF:FE75:C3E1
2001:DB8:CAFE:2::1
Serial0/0/ [up/up]
2001:DB8:CAFE:3::1
R1#
Wait! Two Link-locals are the same!
EUI-64
FF:FE = EUI-64 (most likely)
Serial interfaces will use a MAC address of an Ethernet interface.
Mystery © Copyright sato00

54. Verifying the PC’s Link-Local Address
EUI-64 or random 64-bit value
PC> ipconfig Windows IP Configuration Ethernet adapter Local Area Connection: Connection-specific DNS Suffix .: IPv6 Address : 2001:db8:acad:1:3496:1c51:3f57:fe89 Link-local IPv6 Address : fe80::3496:1c51:3f57:fe89 Default Gateway : fe80::1
Many operating systems will use a random 64-bit Interface IDs for GUA and Link-Local IPv6 Addresses (more in next presentation).

55. Manually Created Link-Local Addresses

56. Link-Local Unicast Address
First 10 bits
Remaining 54 bits
xx xxxx
64-bit Interface ID
FE80::Interface ID
Link-local addresses are created
Automatically :
FE80 (usually) – First 10 bits
Interface ID
EUI-64 (Cisco routers)
Random 64 bits (many host operating systems)
Static (manual) configuration
Only needed on devices where it helps the network administrator remember the address… routers, default gateways.

57. Static Link-Local Addresses
G0/0 FE80::1
S0/0/0
FE80::1
Static addresses are more easily remembered and recognizable.
G0/1
FE80::1 R1
R1(config)#interface gigabitethernet 0/0
R1(config-if)#ipv6 address fe80::1 ?
link-local Use link-local address
R1(config-if)#ipv6 address fe80::1 link-local
R1(config-if)#exit
R1(config)#interface gigabitethernet 0/1
R1(config)#interface serial 0/0/0
R1(config-if)#
Link-Local only Addresses have to be unique on the link!
Have to use link-local option – IOS knows it’s link-local but the first 10 bits (FE80) but it wants to make sure YOU know.
Can use the same for all interfaces – when you want to reach router R1 from any directly connect link using the link-local address we now that it is fe80::1 .
Can also use an address that identifies the router and the link/network. On my network, I use FE80::<RouterID>:<VLAN>

58. Link-Local Addresses: Local and Unique
FE80::2
G0/0 FE80::1
S0/0/0
FE80::1
S0/0/0
FE80::2
G0/1
FE80::1 R1 R2
FE80::2
Link-local addresses have to be unique only on the link but …
Link-local addresses must be unique on the link!
Hosts don’t need to their link-local address statically configured – automatically created is fine.
Can use the same for all interfaces – when you want to reach router R1 from any directly connect link using the link-local address we now that it is fe80::1 .
Can also use an address that identifies the router and the link/network. On my network, I use FE80::<RouterID>:<VLAN>

59. Verifying Link-Local Addresses

60. Verifying Router’s Link-Local Address
R1#show ipv6 interface brief
GigabitEthernet0/0 [up/up]
FE80::FE99:47FF:FE75:C3E0
2001:DB8:CAFE:1::1
<output omitted>
R1#
R1# show ipv6 interface gigabitethernet 0/0
GigabitEthernet0/0 is up, line protocol is up
IPv6 is enabled, link-local address is FE80::FE99:47FF:FE75:C3E0
Global unicast address(es):
2001:DB8:CAFE:1::1, subnet is 2001:DB8:CAFE:1::/64
Also, show running-config

61. Do I Need to Use the ipv6 enable Command?
Router(config)# interface gigabitethernet 0/1
Router(config-if)# ipv6 enable
Router(config-if)# end
Router# show ipv6 interface brief
GigabitEthernet0/ [up/up]
FE80::20C:30FF:FE10:92E1
Router#
Link-local unicast address only
Link-local addresses are automatically created whenever a global unicast address is configured on the interface.
The ipv6 enable command will:
Automatically create a link-local address when there is no global unicast address or static link-local address
Maintain the link-local address even when the global unicast address is removed
Static link-local address is another option

62. Pinging a Link-Local Address?
FE80::1
FE80::1
FE80::2
FE80::2
Ser 0/0/0 :1
G0/0 R1
Ser 0/0/0 :2 R2
2001:DB8:CAFE:2::/64
2001:0DB8:ACAD:1::/64
R1# ping fe80::2
Output Interface: ser 0/0/0
% Invalid interface. Use full interface name without spaces (e.g. Serial0/1)
Output Interface: serial0/0/0
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to FE80::2, timeout is 2 secs:
!!!!!
Must include exit-interface
a link local that an egress interface MUST be associated w/ that use.
(Might also show an example of a PC using a LL to ping a link local address. Rick – Windows 7 didn’t have to specify egress interface)

63. IPv6 Routing Table and Link-Local Addresses
R1# show ipv6 route ospf
O :DB8:CAFE:2::/64 [110/657]
via FE80::2, Serial0/0/0
O :DB8:CAFE:3::/64 [110/1304]
O :DB8:CAFE:A002::/64 [110/1294]
R1#
Link-local addresses are used as next hop addresses
IPv6 dynamic routing protocols like OSPFv3 and EIGRP form neighbor adjacencies and exchange messages using their link-local address as the source address.
More in dynamic routing lessons

64. Thank you and STEAL MY STUFF!