IPv6 Configuration

In IPv4 there are public addresses, where in IPv6 there are global unicast addresses which can trasfer data quicker and are fully hierarchichal, fully routable and can be aggregated. In IPv4 there are also private IP adresses, where in IPv6 there are local addresses which are divided into link local addresses which is very narrow in scope, therefore local to a physical address and site local addresses which are wider in scope and is equivalent to the local address in IPv4, used to access local network but not the public network. Besides unicasts, there are also multicast addresses which starts with the prefix (FF00::/8). There is also anycasts addresses which are assigned to multiple interfaces, and an anycast packet is delivered to only ONE member, which is the closest member in an anycast group that shares the anycast address. The closest member is the first one that was learned by the router on a LAN, and the routing protocol metric on a WAN.

Site Level Aggregator in IPv6 is used to aggregate routes or subnetting in IPv4, but there are more routes in SLA then in IPv4 subnetting. It is 16 bits long and supports over 65.000 subnets.

Autoconfiguration in IPv6 is almost the same as DHCP configuration. There are 2 types of autoconfiguration which are stateless and stateful configuration. Stateful autoconfiguration is also known as DHCPv6 which has the same concepts as DHCP. The host will request an IP address to the server and obtain an information from it. With stateless autoconfiguration the (Duplicate Address Detection) DAD procedure will be executed where the host will configure its own link-local address using FE80:: followed by the MAC address of the host. After configuring its initial IPv6 configuration it will send an Neighbor Solicitation (NS) message to the multicast address FF02::1 (all host multicast address) to check out whether there is another host using the same address. If there is another host using that address (which is supposed not to happen, because each MAC address is unique) the other host will send an Neighbor Advertisement message and the host will disable its MAC address. If this does not happen, than the address is valid and it will send and Router Solicitation (RS) message to the all router multicast address which is FF02::2 to ask the router for other configuration such as the network prefix. The router will send an Router Advertisement to the host and the IPv6 address of the host is complete.

There are also routing protocols in IPv6 some of them are RIP for IPv6/RIPng (new generation), EIGRP for IPv6, ISIS for IPv6, OSPFv3, Multiprotocol BGP/MGBPv4. However, there is no IGRP is not covered in IPv6. To enable Cisco’s router IPv6 routing capabilities use the command config#ipv6 unicast-routing.

For OSPFv3, the process is enable per interfaceas opposed to global configuration in OSPFv2. To enable it on an interface use the command (config-if)#ipv6 ospf area . To create a router ID if there is none, use the command (config-router)#router-id . Other notes for OSPFv3 is that OSPFv3 NBMA configuration still needs neighbor statements and point-to-point and point-to-multipoint configurations do not elect DR and BDR such as in IPv4. OSPFv3 allows a link to be a part of multiple instances, whereas in IPv4 to only 1 instance. OSPFv3 headers are smaller because they have no authentication fields. The OSPF reserved address 224.0.0.5 in IPv6 is FF02::5 and 224.0.0.6 in IPv6 is FF02::6.

Basic configuration to create an adjecency on the routers using ospf is to configure the following on the adjacent routers:

(config)#ipv6 unicast-routing

(config)#ipv6 cef

(config)#ipv6 router ospf 1

(config-rtr)#router-id

(config)#int

(config-if)#ipv6 ospf area

To verify, the following commands can be used:

#show ipv6 ospf neighbor or #show ipv6 ospf neighbor detail

#show ipv6 ospf interface or #show ipv6 ospf interface

To clear/reset the configuration use the command #clear ipv6 ospf process

There are 3 known ways to migrate from IPv4 to IPv6 which are dual stack, 6-4 tunnel and NAT PT (Network Address Translation – Protocol Translation). With dual stack, an interface has 2 IP addresses which are IPv4 address and IPv6 address. With a 6-4 tunnel, an IPv6 packet is encapsulated to an IPv4 packet and sent through the IPv4 network. When it reaches the end, it will decapsulate the packet and sent through the IPv6 network again using the original IPv6 address. This is a scalable and easy solution, and the network will be torn down if the session ends.The edge routers will have a unique address which is 2002:IPv4 address of the router in hex ::/48 prefix. NAT PT work similar to original NAT, except that NAT PT routers translate IPv4 addresses to IPv6 addresses and in reverse.

To create a tunnel use the command:

(config)#int

(config-if)#ip address

(config-if)#int tunnel

(config-if)#ipv6 address 2002:HHHH:HHHH::/48

-- 13 April 2011 --

IPv6 header, IPv4 to IPv6 conversion, IPv6 addressing, zero compression & leading zero compression

Slowly but sure, there is a migration from IPv4 to IPv6 because of the shortage of IP address. There has been previous tricks being done to avoid this migration such as doing NAT and DHCP, but as the number of devices that needs IP addresses increases and to provide a more secure network, migration to IPv6 is necessary. The major difference in IPv4 and IPv6 is that IPv6 has more addresses available then IPv4. IPv4 uses 32 bits that is divided into 4x8bits. IPv6 uses 128 bits that is divided into 8x16bits hexadecimal. An example of IPv4 is 123.145.167.189 where an example of IPv4 is 1234:5678:9ABC:DEF0:1234:5678:9ABC:DEF0. IPv6 has several important uses such as Mobile IP, which is usually found on GPS, that allows devices to move without losing its connectivity and IPSec which is a protocol suite to secure IP communications.

IPv4 and IPv6 have different header fields (bits) with the comparison as below:

IPv4 (160 bits) = Version(4), IHL(4), Type of Service(8), Total Length(16), Identification(16), Flags(4), Fragment Offset(12), Time to Live(8), Protocol(8), Header Checksum(16), Source Address(32) and Destination Address(32).

IPv6 (320 bits)=Version(4), Traffic Class(8), Flow Label(20), Payload Length(16), Next Header(8), Hop Limit(8), Source Address(128), Destination Address(128)

In total, 3 fields are still the same (Version, Source Address and Destination Address), 5 fields removed from IPv4 to IPv6 (IHL, Identification, Flags, Fragment Offset, Header Checksum), 1 new field in IPv6 (Flow Label) and 4 fields has modified names but almost the same function (Type of Service = Traffic Class, Total Length = Payload Length, Protocol = Next Header, TTL = Hop Limit)

IPv4 uses a range from 0-255 decimal from binary octets, whereas IPv6 has a range of 0000-FFFF hexadecimal. To convert IPv4 compatible adresses, each 2 hexadecimal numbers in IPv6 represent an octet in IPv4. The formula for converting IPv6 into IPv4 is (first digit*16)+second digit. To convert back from IPv4 to IPv6 divide the IPv4 number by 16 (first digit) and the remaining value as the second digit.

For example:

IPv4 to IPv6: 123.145.167.189 = (7*16)+11 - (9*16)+1 - (10*16)+7 - (11*16)+13 = 7B91:A7BD

IPv6 to IPv4 : 65AB:4F23 = (6*16)+5 - (10*16)+11 - (4*16)+15 - (2*16)+3 = 101.171.79.35

IPv6 has 128 bits which are considered very long. There are 2 methods to shorten IPv6 address which are leading zero compression and zero compression. In leading zero compression, all zeros leading in a field can be omitted, but if there are 4 hexadecimal zeros on the field, one zero must be still left. In zero compression, several fields that has only zeros, can be joined together with the symbol :: However, zero compression can only be applied ONCE in an IPv6 address, whereas leading zero compression can be implemented multiple times.

For example:

12AB:0000:0000:0000:0012:023F:0000:FAF8 can be written as below:

Using leading zero compression ==> 12AB:0:0:0:12:0:FAF8

Using zero compression ==> 12AB::12:0:FAF8

There are several addresses with the following initial bits to remember which are:

001 (starting with 0010 hex = 2 decimal or 0011 hex = 3 decimal) = global address

1111 1111 (FF00::/8 hex) = multicast (in IPv4 = 224.0.0.0 – 239.255.255.255)

1111 1110 1 (FEXX) = private address

1111 1110 1100 (FEC0) = site local

1111 1110 1000 (FE80) = link local

::x.x.x.x = IPv4 compatible address

0:0:0:0:0:0:0:1 or ::1 = loopback address (in IPv4 = 127.0.0.1)

0:0:0:0:0:0:0:0 or ::/128 = unspecified address

::/0 = default route

-- 13 April 2011 --