4: ipv6 global unicast addresses

4: Global Unicast Addresses (GUA)

Rick GrazianiCabrillo College

[email protected]

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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

4.1: Purpose and Format of GUA

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IPv6 Address TypesIPv6 Addresses

FF00::/8 FF02::1:FF00:0000/104

::/128::1/1282000::/3 FE80::/10 FC00::/7 ::/80

Unicast Multicast Anycast

Assigned Solicited Node

Global Unicast Link-Local Loopback Unspecified Unique

LocalEmbedded

IPv4

IPv6 does not have a “broadcast” address.

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IPv6 Source and Destination Addresses• IPv6 Source – Always a unicast

(link-local or GUA)• IPv6 Destination – Unicast,

multicast, or anycast.

IPv4

IPv6

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Global Unicast Address

• 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.

IPv6 Internet

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Global Unicast Address RangeInterface IDSubnet IDGlobal Routing Prefix

001 0010 0000 0000 0000 :0011 1111 1111 1111 :

IANA’s allocation of IPv6 address space in 1/8th sections

Range: 2000: 3FFF:

• Global Unicast Address (GUA)• 2000::/3 • Range 2000::/64 thru 3fff:fff:fff:fff::/64• 1/8th of IPv6 address space

First hextet

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Global Unicast Address Range

• Except under very specific circumstances, all end users will have a global unicast address.• Note: A host (an interface) can potentially have multiple IPv6

addresses on the same or different networks.• 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

Interface IDSubnet IDGlobal Routing Prefix

001 Range: 2000::/64 thru 3fff:fff:fff:fff::/64

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Parts of a Global Unicast Address

• 64-bit Interface ID = 18 quintillion (18,446,744,073,709,551,616) devices/subnet• 16-bit Subnet ID (initially recommended) = 65,536 subnets

IPv4 Unicast Address

32 bits

Network portion Host portionSubnet portion

/?

IPv6 Global Unicast Address

128 bits

Global Routing Prefix Interface ID16-bit Subnet ID

/64/48

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/64 Global Unicast Address and the 3-1-4 Rule

Interface IDSubnet IDGlobal Routing Prefix

2001 : 0DB8 : CAFE : 0001 : 0000 : 0000 : 0000 : 0100

3 + 1 = 4 (/64) : 42001:0DB8:CAFE:0001:0000:0000:0000:0100/642001:DB8:CAFE:1::100/64

16 bits 16 bits 16 bits 16 bits 16 bits 16 bits 16 bits 16 bits

3 1 4

/48 /64

4.2: Subnetting IPv6

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Subnetting IPv6Can 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

3-1-4 Rule

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For Demonstration Purposes OnlyExtending the Subnet ID

Prefix

2001 : 0DB8 : CAFE : 0000 : 0000 : 0000 : 0000 : 00002001 : 0DB8 : CAFE : 0000 : 0001 : 0000 : 0000 : 00002001 : 0DB8 : CAFE : 0000 : 0002 : 0000 : 0000 : 0000 thru2001 : 0DB8 : CAFE : FFFF : FFFE : 0000 : 0000 : 00002001 : 0DB8 : CAFE : FFFF : FFFF : 0000 : 0000 : 0000

Global Routing Prefix Subnet-ID Interface ID

Global Routing Prefix48-bit Interface ID32-bit Subnet ID

/80/48

Global Routing Prefix Interface ID16-bit Fixed Subnet ID

/64/48

Note:• It is highly recommended to NOT subnet into the /64

interface ID portion of the address to configure subnets. • The only exception would be for network infrastructure

(router-to-router links, router-to-switch links, etc.).• Networks with an end system attached should be a /64.

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For Demonstration Purposes OnlySubnetting on a Nibble Boundary

/68 Prefix

Subnetting on a nibble (4 bit) boundary makes it easier to list the subnets: /64, /68, /72, etc.2001:0DB8:CAFE:0000:0000::/682001:0DB8:CAFE:0000:1000::/682001:0DB8:CAFE:0000:2000::/68 through2001:0DB8:CAFE:FFFF:F000::/68

/68

Global Routing Prefix Interface IDSubnet ID/68/48

20 bits 60 bits

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For Demonstration Purposes OnlySubnetting within a Nibble

/70 Prefix

2001:0DB8:CAFE:0000:0000::/70

2001:0DB8:CAFE:0000:0400::/70

2001:0DB8:CAFE:0000:0800::/70

2001:0DB8:CAFÉ:0000:0C00::/70

Global Routing Prefix Interface IDSubnet ID/70/48

22 bits 58 bits

0000

0100

1000

1100

Four Bits: • Two leftmost bits:

Subnet-ID

• Two rightmost bits: Associated with the Interface ID

Binary

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• RFC 6164 - Using 127-Bit IPv6 Prefixes on Inter-Router Links• Ping-Pong Attack • Neighbor Cache Exhaustion Issue

• There are mitigation techniques for both.• If you want to use a /127, reserve a separate /64 for each /127…. Really!

Do I Need the IPv6 Equivalent to an IPv4 /30?

Global Routing Prefix Subnet ID/127/48

79 bits 1bit

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2001:DB8:CAFE:F000::/64

2001:DB8:CAFE:F000::0/127

2001:DB8:CAFE:F000::1/127

2001:DB8:CAFE:F001::/64

2001:DB8:CAFE:F001::0/127

2001:DB8:CAFE:F001::1/127

Allocate Separate /64’s


79 bits 1bit

0 or 12001:DB8:CAFE:F000::/64

2001:DB8:CAFE:F001::/64

2001:DB8:CAFE:F002::/64

2001:DB8:CAFE:F003::/64

And so on...

For each /127 allocate an entire /64:

000F000F0013 bits

All 0s “::” can be confusing

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Use a Different Last 3 bits for the Subnet ID


79 bits 1bit

0 or 12001:DB8:CAFE:F000::/64

2001:DB8:CAFE:F000::A/127

2001:DB8:CAFE:F000::B/127

2001:DB8:CAFE:F001::/64

2001:DB8:CAFE:F001::A/127

2001:DB8:CAFE:F001::B/127

101F000F0013 bits

Be careful which two interfaces addresses you choose.

::9 and ::A are not on the same /127 subnet

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IPv6 Addressing Plan• IPv4 subnetting is used to help

conserve IPv4 address space.• Managing a limited space• VLSM• /30s for point-to-point links

• IPv6 address conservation does not need to be as aggressive as IPv4.

• Developing an address plan that is:• Makes sense.• Easy to manage.

• NANOG BCOP: IPv6 Subnetting • Cisco: IPv6 Address Guide• RIPE NCC: Preparing an IPv6

Addressing Plan - RIPE Network

RFC 1878 VLSM

4.3: IPv6 Address Allocation

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/48 /64/32/23

*RIR

*ISP Prefix

*Site Prefix

Subnet Prefix

* This is a minimum allocation. The prefix-length may be shorter if it can be justified.

/56

Possible Home Site Prefix

I am getting a /64 at homeGlobal Routing Prefix

Interface IDSubnet IDSub

IPv6 Address Allocation

Internet Service Provider

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Global Routing Prefix determines number of /64 subnets *

2001:DB8:0000:0000:0000:0000:0000:0000

/32 = 65,536 /48’s

/64

/60 = 16 /64’s

/56 = 256 /64’s

/52 = 4,096 /64’s

/48 = 65,536 /64’s (Many sites will get this prefix length)

64-bit Interface ID

/44 = 1,048,576 /64’s/40 = 16,777,216 /64’s

/36 = 268,435,456 /64’s

/32 = 4,294,967,296 /64’s

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PI versus PA Address Space

Provider Independent (PI) Address Space• Address space that is assigned by the RIR. • Remains assigned to the customer regardless of provider• No prefix renumbering needed if change providersProvider Aggregatable (PA) Address Space• Address space that is typically assigned by an ISP to a customer. • Change provider, must get new address space• Customer must do prefix renumbering (Helpful IETF RFCs)

Global Routing Prefix Interface ID

/48/32

Subnet ID

ISPRIR

4.4: Configuring a Static GUA

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Configuring a Global Unicast Address

• Details, including the operations and configurations of SLAAC (Stateless Address Autoconfiguration) in Lesson 7 and DHCPv6 in Lessons 8.

Global Unicast

Manual Dynamic

Static IPv6 unnumbered

Static + EUI 64

SLAAC DHCPv6

SLAAC + DHCPv6

Similar to IPv4 unnumbered

Stateless Stateful

Overview only

DHCPv6-PD

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• 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.

No space

R1(config)#interface gigabitethernet 0/0R1(config-if)#ipv6 address 2001:db8:cafe:1::1/64R1(config-if)#no shutdownR1(config-if)#exit

2001:DB8:CAFE:3::/642001:DB8:CAFE:1::/64

2001:DB8:CAFE:2::/64

G0/0:1:1

G0/1:1S0/0/0

:100

:100

Static GUA Configuration

R1

A

B

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2001:DB8:CAFE:3::/642001:DB8:CAFE:1::/64

2001:DB8:CAFE:2::/64

G0/0:1:1

G0/1:1S0/0/0

:100

:100

Static GUA Configuration

R1

A

B

R1(config)#interface gigabitethernet 0/1 R1(config-if)#ipv6 address 2001:db8:cafe:2::1/64R1(config-if)#no shutdownR1(config-if)#exitR1(config)#interface serial 0/0/0 R1(config-if)#ipv6 address 2001:db8:cafe:3::1/64R1(config-if)#no shutdownR1(config-if)#exit

I love the 3-1-4 rule and

subnetting IPv6!

The ipv6 unicast-routing global configuration command is required for forward IPv6 packets – it is not required to configure IPv6 addresses.

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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!

2001:DB8:CAFE:3::/642001:DB8:CAFE:1::/64

2001:DB8:CAFE:2::/64

G0/0:1:1

G0/0:1S0/0/0

:100

:100

Verifying Address Using

Running Configuration

R1

A

B

IPv4 address

IPv6 address

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R1# show ipv6 interface briefGigabitEthernet0/0 [up/up] FE80::FE99:47FF:FE75:C3E0 2001:DB8:CAFE:1::1! <output omitted>

Global unicast addressLink-local 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.

Verifying Unicast Addresses on R1

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Same as IPv4 devices:• Servers, printers, routers, etc.

Can also be a link-local unicast address of the router.

Static GUA Configuration on PC

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PCA> ipconfigWindows IP ConfigurationEthernet 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

Verifying Unicast Addresses on PC

• Link-local addresses are created automatically.• Recent Microsoft operating systems use a random 64-bit Interface ID for link-

local address… (coming soon)

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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=1msReply from 2001:db8:cafe:1::1: time=1msReply from 2001:db8:cafe:1::1: time=1msReply 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 = 1msPCA>

Verifying IPv6 Connectivity

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Router(config)# ipv6 general-prefix ? WORD General prefix name

Router(config)# ipv6 general-prefix MyGUA 2001:db8:cafe::/48Router(config)# interface gigabitethernet 0/0Router(config-if)# ipv6 address MyGUA 0:0:0:88::1/64Router(config-if)# no shutdownRouter(config-if)# exitRouter(config)# interface gigabitethernet 0/1Router(config-if)# ipv6 address MyGUA 0:0:0:99::1/64Router(config-if)# no shutdownRouter(config-if)# endRouter# show ipv6 interface briefGigabitEthernet0/0 [up/up] FE80::7EAD:74FF:FECC:5380 2001:DB8:CAFE:88::1GigabitEthernet0/1 [[up/up] FE80::7EAD:74FF:FECC:5381 2001:DB8:CAFE:99::1<output omitted>

IPv6 General Prefix: Making your life easier

• The general-prefix option can be used as a short-cut or alias for just about any command requiring an IPv6 address, addressing, ACLs, etc.

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Router(config)# no ipv6 general-prefix MyGUA 2001:db8:cafe::/48Router(config)# ipv6 general-prefix MyGUA 2001:db8:beef::/48Router(config-if)# endRouter# show ipv6 interface briefGigabitEthernet0/0 [up/up] FE80::7EAD:74FF:FECC:5380 2001:DB8:BEEF:88::1GigabitEthernet0/1 [[up/up] FE80::7EAD:74FF:FECC:5381 2001:DB8:BEEF:99::1<output omitted>Router# show running-config<partial output> ipv6 general-prefix MyGUA 2001:DB8:BEEF::/48!interface GigabitEthernet0/0 ipv6 address MyGUA ::88:0:0:0:1/64!interface GigabitEthernet0/1 ipv6 address MyGUA ::99:0:0:0:1/64!

IPv6 General Prefix: Renumbering

• It is also greatly simplifies network renumbering and allows for automated prefix definition.

4.5: Configuring a Static GUA with EUI-64

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Configuring a Static GUA + EUI-64

Global Unicast

Manual Dynamic


Static + EUI 64

SLAAC DHCPv6

SLAAC + DHCPv6


Stateless Stateful

DHCPv6-PD

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R1(config)# interface gigabitethernet 0/1R1(config-if)# ipv6 address 2001:db8:cafe:99::/64 ? eui-64 Use eui-64 interface identifier <cr>

R1(config-if)# ipv6 address 2001:0db8:cafe:99::/64 eui-64R1(config-if)#

2001:DB8:CAFE:99::/64

G0/1 R1


All 0s is ok!

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

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Modified EUI-64 Format (Extended Unique Identifier–64)

00 03 6B E9 D4 80

OUI (24 bits) Device Identifier (24 bits)

00 03 6B E9 D4 80FF FE

03 6B E9 D4 80FF FE0000 000000 U/L bit flipped

0000 0010

02 03 6B E9 D4 80FF FE

Insert FF-FE

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R1(config)# interface gigabitethernet 0/1R1(config-if)# ipv6 address 2001:db8:cafe:99::/64 eui-64

R1# show interface gigabitethernet 0/1GigabitEthernet0/1 is up, line protocol is up Hardware is AmdFE, address is 0003.6be9.d480 (bia 0003.6be9.d480)<output omitted>

R1# show ipv6 interface gigabitethernet 0/1GigabitEthernet0/1 is up, line protocol is up IPv6 is enabled, link-local address is FE80::203:6BFF:FEE9:D480 Global unicast address(es): 2001:DB8:CAFE:99:203:6BFF:FEE9:D480, subnet is 2001:DB8:CAFE:99::/64<output omitted>


64-bit prefix from configuration64-bit Interface ID using EUI-64

EUI-64: 48-bit MAC address with FFFE (16 bits) inserted and 7th bit flipped

4.6: Overview of Dynamic IPv6 Address Allocation (SLAAC and DHCPv6)

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Dynamic IPv6 Address Allocation

Global Unicast

Manual Dynamic


Static + EUI 64

SLAAC DHCPv6

SLAAC + DHCPv6


Stateless Stateful

Overview only

DHCPv6-PD

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DHCP Server


DHCP Client

I need IPv4 addressing information from a DHCP server.

Here is your IPv4 address, subnet mask,

default gateway and DNS server addresses.

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ICMPv6Internet Control Message

Protocol for IPv6• ICMPv6 than just “messaging” but “how

IPv6 conducts business”.• ICMPv6 Neighbor Discovery (RFC

4861) – used in dynamic address allocation.

• More later!

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Once again… ICMPv6 Neighbor DiscoveryICMPv6 informational messages used by Neighbor Discovery (RFC 4861):

• Router Solicitation Message• Router Advertisement Message

• Used for dynamic address allocation.

• Neighbor Solicitation Message• Neighbor Advertisement Message

• Used with address resolution (IPv4 ARP) and with DAD

• Redirect Message (Similar to ICMPv4)

Router-Device Messaging

Device-Device Messaging

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It Begins with the RA Message

• 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.

DHCPv6 Server

ICMPv6 Router Advertisement

ICMPv6 Router Solicitation

Multicast: To all IPv6 routers, I need

IPv6 address information

Multicast: To all IPv6 devices,

let me tell you how to do this …

I might not even be needed.

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It Begins with the RA Message

Router Advertisement (RA) Message• Part of ICMPv6 (Internet Control Message Protocol for IPv6)• RA messages are sent by an “IPv6 router”, ipv6 unicast-routing command

• Forwards IPv6 Packets• Enables IPv6 dynamic routing• Sends ICMPv6 Router Advertisements

• Routers can be configured with IPv6 addresses without being an IPv6 router.• IPv6 static routes can be configured but the router will only forward locally

generated packets – it will not forward packets that transit through the router.

DHCPv6 Server

ICMPv6 Router Advertisement

Router(config)# ipv6 unicast-routing

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Router Advertisement: 3 Options

DHCPv6 Server

RA

Router(config)# ipv6 unicast-routing

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.”

DHCPv6

Option 1 and 2: Stateless Address Autoconfiguration• DHCPv6 Server does not maintain state of addressesOption 3: Stateful Address Configuration• Address received from DHCPv6 Server

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Global Unicast

Manual


Static + EUI 64

SLAAC DHCPv6

SLAAC + DHCPv6


Stateless Stateful

DHCPv6-PD

• ICMPv6 – Lesson 9• ICMPv6 Neighbor Discovery including packet captures – Lesson 10

Dynamic

Stateful

Lesson 8

Lesson 7

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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

4: Global Unicast Addresses (GUA)

Rick GrazianiCabrillo College

[email protected]

4: ipv6 global unicast addresses

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