IPv6 Addressing Overview IPv6 increases the number of address bits by a factor of 4, from 32 to 128, providing a very large number of addressable nodes. IPv4 = 32 bits 11111111.11111111.11111111.11111111 IPv6 = 128 bits With IPv4, some number of bits on the left side of the 32 bit address represent the network and possibly the subnet. The remaining bits represent a host on that network/subnet. With IPv6, normally the first 64 bits represent the network/subnet address and the remaining 64 bits represent the host address. This will be covered in greater detail later.

2001:0DB8:AAAA:1111:0000:0000:0000:0100/64 2001 : 0DB8 : AAAA : 1111 : 0000 : 0000 : 0000 : 0100

Decimal Hex Binary 0000 1 0001 2 0010 3 0011 4 0100 5 0101 6 0110 7 0111 8 1000 9 1001 10 A 1010 11 B 1011 12 C 1100 13 D 1101 14 E 1110 15 F 1111

Abbreviating IPv6 Addresses Leading 0s within each set of four hexadecimal digits can be omitted. 09C0 = 9C0 0000 = 0 A pair of colons (“::”) can be used, once within an address, to represent any number (“a bunch”) of successive zeros. IPv6 addresses can be very long and confusing to look at. Fortunately, in many cases, they can be abbreviated by suppressing leading zeros and representing 4 consecutive zeros within a 4-character Hex field with a single zero. A pair of colons can be used to represent consecutive Hex field strings of zeros. This greatly simplifies the writing of IPv6 addresses since the eight 16-bit Hex fields can be compressed when there are a number of consecutive zeros in the address. This happens frequently, especially with the network portion of the address.

IPv6 Address Abbreviation Example 2031:0000:130F:0000:0000:09C0:876A:130B 2031: 0:130F: 0: 0: 9C0:876A:130B 2031:0:130F:0:0:9C0:876A:130B 2031:0:130F:0:0:9C0:876A:130B This example shows how an IPv6 address can be abbreviated or compressed by converting four hex digit zeros to a single zero, elimination of leading zeros and the representation of multiple sets of contiguous zeros as a double colon. Remember that the double colon can be used only once in an IPv6 address. 2031:0:130F::9C0:876A:130B

More IPv6 Address Abbreviation Examples FF01:0000:0000:0000:0000:0000:0000:1 = FF01:0:0:0:0:0:0:1 = FF01::1 E3D7:0000:0000:0000:51F4:00C8:C0A8:6420 = E3D7::51F4:C8:C0A8:6420 Shown here are some additional examples of how IPv6 addresses with leading and contiguous zeros can be abbreviated. 3FFE:0501:0008:0000:0260:97FF:FE40:EFAB = 3FFE:501:8:0:260:97FF:FE40:EFAB = 3FFE:501:8::260:97FF:FE40:EFAB

IPv6 Address Components An IPv6 address consists of two parts: A subnet prefix An interface ID IPv6 = 128 bits 11111111.11111111.11111111.11111111 Subnet prefix Interface ID

Identify the Network Bits and Host or Interface Bits 2001:DB8:CAFÉ:1111::1/64 Answer – network bits = 64, host bits = 64 Network Portion = 2001:DB8:CAFE:1111 Host Portion = 0000:0000:0000:0001 2001::1/96 Answer – network bits = 96, host bits = 32 Network Portion = 2001:0:0:0:0:0 Host portion = 0:1

Identify the Network Bits and Host or Interface Bits 2001::1/80 Answer – network bits = 80, host bits = 48 Network Portion = 2001:0:0:0:0 Host Portion = 0:0:1 2001::1/16 Answer – network bits = 16, host bits = 112 Network Portion = 2001 Host portion = 0:0:0:0:0:0:1

Subnet Prefix The prefix length is almost always /64. However, IPv6 rules allow for either shorter or longer prefixes Deploying a /64 IPv6 prefix on a device recommended. Allows Stateless Address Auto Configuration (SLAAC) - (later topic)

IPv6 Address Types Address Type Description Topology Unicast Multicast “One to One” An address destined for a single interface. A packet sent to a unicast address is delivered to the interface identified by that address. Multicast “One to Many” An address for a set of interfaces (typically belonging to different nodes). A packet sent to a multicast address will be delivered to all interfaces identified by that address. Anycast “One to Nearest” (Allocated from Unicast) An address for a set of interfaces. In most cases these interfaces belong to different nodes. created “automatically” when a single unicast address is assigned to more than one interface. A packet sent to an anycast address is delivered to the closest interface as determined by the IGP.

2001 : 0DB8 : AAAA : 1111 : 0000 : 0000 : 0000 : 0100

Special IPv6 Addresses IPv6 Address Description ::/0 All networks and used when specifying a default static route. It is equivalent to the IPv4 quad-zero (0.0.0.0) ::/128 Unspecified address and is initially assigned to a host when it first resolves its local link address ::1/128 Loopback address of local host Equivalent to 127.0.0.1 in IPv4 FE80::/10 Link-local unicast address Similar to the Windows autoconfiguration IP address of 169.254.x.x FF00::/8 Multicast addresses All other addresses Global unicast address SCRIPT: A closer look at some of the special IPv6 addresses and prefixes reveals similarities to IPv4. The ones shown here are particularly helpful to remember. For example, IPv6 address ::/0 is analogous to IPv4 quad zero address 0.0.0.0 for use in defining static default routes. IPv6 ::1/128 is analogous to IPv4 local host loopback address 127.0.0.1.

Link-local Address Dynamically created on all IPv6 interfaces by using a specific link-local prefix (FE80::/10) and a 64-bit interface identifier Used for automatic address configuration, neighbor discovery, and router discovery. Can serve as a way to connect devices on the same local network without needing global addresses When communicating with a link-local address, you have to specify the outgoing interface. Can recognize because is starts with FE80

Verifying IPv6 Command Description show ipv6 interface [brief] [type number] [prefix] Displays the status of interfaces configured for IPv6. The brief keyword displays a brief summary. The prefix keyword displays the IPv6 neighbor discovery prefixes that are configured on a specified interface. show ipv6 routers [interface-type interface-number] [conflicts] Displays IPv6 router advertisement information received from on-link routers (those locally reachable on the link). The conflicts keyword displays information about routers advertising parameters that differ from the advertisement parameters configured for the specified interface on which the advertisements are received. show ipv6 neighbors [interface-type interface-number | ipv6- address | ipv6-hostname | statistics] Displays IPv6 neighbor discovery cache information for the specified neighbors. The optional statistics parameter displays neighbor discovery cache statistics. SCRIPT: Many IPv6 show commands are available to verify IPv6 implementations. Most of them are similar to their IPv4 counterparts with the only difference being the replacement of the keyword “ip” with “ipv6” in the command. For example, the IPv6 version of the IPv4 show ip interface command is show ipv6 interface. Some useful IPv6 show commands are listed here. Note that the commands show ipv6 routers and show ipv6 neighbors are unique to IPv6.

Also required to support autoconfiguration of end devices. Enable IPv6 Routing Enable the forwarding of IPv6 unicast datagrams. ipv6 unicast-routing This command is required before configuring any form of IPv6 routing (static or dynamic) Also required to support autoconfiguration of end devices. The no ipv6 unicast-routing disables IPv6 routing capabilities of the router. SCRIPT: The Cisco IOS ipv6 unicast routing command is required before implementing either static or dynamic routing with IPv6 global unicast addresses. The command is not needed before configuring IPv6 interface addresses. It is also required for the interface to provide stateless auto-configuration. Configuring no ipv6 unicast-routing disables the IPv6 routing capabilities of the router and the router acts as an IPv6 end-station.

Common Practice Normally you request your address from an ISP – and they generally give you at least a /48 prefix. So, you have /80 bits to use as you need to. The recommendation from RFC4291 is a /64 prefix being the smallest prefix. If we use 1 hextet for subnetting (16 bits) – that is half the entire IPv4 address space Or host bits 2001 : 0DB8 : AAAA : 1111 : 0000 : 0000 : 0000 : 0100

Common Practice Say we are assigned: 2003:db8:4567:0000::/48 from our ISP (Can’t change the first 3 hextets – just like IPv4) So we now have that “4th” hextet to do what we want to with (always) So now our total network bits are 64, because of that 4th hextet How we manage it would depend.

Break Down the 4th Hextet 2003:db8:4567:0 0 0 0:/64 – change hex to binary 0000 0000 0000 0000 Now we can use these “nibbles” for management. We really wouldn’t even have to use all 16 bits for subnetting. We could use /52 or /56 or /60 If we used /56 we could only use the first 2 nibbles. 2003:db8:4567:1000::/56 2003:db8:4567:2000::/56 2003:db8:4567:3000::/56

Private Addresses? Sort of They are called Unique Local Addresses (ULA) – not created automatically like link-local addresses IPv4 10.0.0.0 – 10.255.255.255 172.16.0.0 – 172.31.255.255 192.168.0.0 192.168.255.255 IPv6 FC00::/7 – not really that useful – but can be used if needed