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To cover the IP addressing issues by facing the network administrators today, consider that the IPv4 address spaced allows approximately 4,294,967,296 unique addresses. Of these, only 3.7 billion addresses that are been assigned because the IPv4 addressing system separates the address into classes and reserves addresses for multicasting, testing, and other specified uses.
The past decade, the Internet community has been analyzed IPv4 addresses exhaustion and publishes mountains of reports. Some reports predicted IPv4 address exhaustion by 2010, and others said it will not happen until 2013. The growth of the Internet, matched by increasing the computing power, has extended the reach of IP-based applications.
The pool of numbers is shrinking for the following reasons:
Population growth - The population of the internet has been growing. In Nov 2005, Cisco has been estimate that there were about millions of users. This number has twice since then. In addition, the users stayed no longer, are been reserved the IP addresses for longer times and as been reaching more and more peers every day.
Mobile users - Industries have been produce more than 1 billion cell phones. More than twenty million IP-enabled mobile devices, included personal digital assistants (PDAs), pen tablets, notepads, and barcode readers, have been produced. More and more IP-enabled mobile devices are coming online daily. Old cell phones didn't need IP addresses, but new ones need.
Transportation - There will be more than 1 billion auto-mobiles by 2008. Latest models are IP-enabled to provide remote monitoring to allow timely maintenance and support. More than those carriers, including ships at ocean, will use similar services.
Consumer electronics - The newest modern house appliances allow remote monitoring which is used by IP technology. DVRs which download and update program guided via Internet are an example. House networking can connect these widgets.
The ability to scaled networks for future requirements needs an unlimited support of IP addresses and improved mobility that only DHCP and NAT cannot converge. IPv6 converges the increasingly complex needs of hierarchical addressing that IPv4 doesn't allow.
Given the very big installed foundation of IPv4 in the world, it isn't so difficult to appreciate that transitioning to IPv6 from IPv4 deployments is a great challenge. Nevertheless, there are a many options of techniques, included an auto-configure option, to make the transition easier. The transition mechanism we used depends on the needs of our network.
The picture compared to the binary and alphanumeric representations of IPv4 and IPv6 addresses. IPv6 address is a 128-bit binary value, which can be showed as 32 hexadecimal digits. IPv6 should allow enough addresses for future the growing of internet needs for next many years. There may be enough IPv6 addresses to allocate more than the all IPv4 Internet address space to everybody on the world.
2. The history and the current technology
IPv6 won't be existed were it not for the recognized reduction of available IPv4 addresses. Nevertheless, beyond the increased IP address space, the growth of IPv6 has been presented chances to apply lessons learn from the limitations of IPv4 to be created a protocol with new and improvement features.
A simplify that the header of architecture and protocol operation translates into reducing the operational expenses. Built-in security features mean easier security practices that are sorely lacking in many current networks. Even so, may be the most important improvement provide by IPv6 is the address auto-configuration features it has.
Address auto-configuration also means more robust plug-and-play network connectivity. Auto-configuration supports consumers who can have any addition of modern devices such as computers, printers, digital cameras, digital radios, IP phones and Internet-enabled household appliances connected to their home networks. Most of manufacturers already integrated IPv6 into their products.
Many of the enhancements that IPv6 offers are explained in this part as following:
Enhanced IP addressing
Mobility and security
2.1 Enhanced IP Addressing
A bigger address space is offered many enhancements, including:
Improved world wide reachability and flexibility.
Better collection of IP prefixes announced in routing tables.
Multi-homed hosts, Multi-homing are a mechanism to increase the dependability of the Internet connection on an IP network. With IPv6, a host can get a lot of IP addresses over only one physical link. A host can be connecting to various ISPs.
Auto-configuration can include data link layer addresses in address space.
More plug-and-play functions for more modern devices.
Public-2-private, end-2-end readdressing can do without address translation. That makes peer-to-peer (P2P) networking more useable and easier to configure.
Simplified techniques for address renumbering and modification.
2.2 Simplified Header
The picture compares the simplified IPv6 header structure to the IPv4 header. The IPv4 header uses twenty octets and twelve basic header fields, followed by an options field and a data portion. The IPv6 header has 40 octets, 3 IPv4 basic header fields, and 5 additional header fields.
The IPv6 simplified header offers various advantages over IPv4:
Better routing efficiency for performance and forwarding-rate scalability
There is no broadcasts and so no potential threat of broadcast storms
There is no require for processing checksums
More simplified and more efficient extension header techniques
Flow labels for per-flow processing process with no requirement to open the transport inner packet to identify the several traffic flows
2.3 Enhanced Mobility and Security
Mobility and security will help certain compliance with mobile IP and IP Security (IPsec) standards functionality. Mobility changes people with mobile network devices with wireless connectivity to move around in networks.
IETF Mobile IP standard is useable for both IPv4 and IPv6. That standard enables mobile devices to move without interrupts in established network connections. Mobile devices will use a home address and a care-of address to achieve this mobility. With IPv4, those addresses are configured by manually. With IPv6, the configurations are dynamically done, giving Ipv6-ready devices built-in mobility.
IPsec can use in the both of IPv4 and IPv6. While the functionalities are essentially identical in both environments, IPsec is required in IPv6, to make the IPv6 Internet more secure.
3. IPv6 Addressing
3.1IPv6 Address Representation
Everybody knows the 32-bit IPv4 address as a series of four 8-bit fields, separated by dots. However, larger 128-bit IPv6 addresses need a different representation because of their size. IPv6 addresses use colons to separate entries in a series of 16-bit hexadecimal.
The picture shows the address 2031:0000:130E:0000:0000:09C0:876A:130B. IPv6 doesn't need explicit address string notation. The picture shows how to shorten the address by applying the following guidelines:
Leading zeros in a field are optional.
Successive fields of zeros can represent as two colons "::". However, this shorthand method can only be used once in an address.
An unspecified address is written as "::" because it contains only zeros.
Using the "::" notation greatly reduces the size of most addresses as shown. An address parser identifies the number of missing zeros by separating any two parts of an address and entering 0s until the 128 bits are complete.
3.2 IPv6 Addresses
3.2.1 IPv6 Global Unicast Address
IPv6 has an address format that enables aggregation upward eventually to the ISP. Global unicast addresses normally consists of a 48-bit global routing prefix and a 16-bit subnet ID. Individual organizations can be used a 16-bit subnet field to make their own local addressing hierarchy. This field provides an organization to use up to 65,535 individual subnets.
At the top of the picture, it can be seen how additional hierarchy is added to the 48-bit global routing prefix with the registry prefix, ISP Prefix, and site prefix. The current global unicast address which is assigned by the IANA uses the range of addresses that start with binary value 001 (2000::/3), that is 1/8 of the total IPv6 address space and is the biggest block of assigned addresses. The IANA is allocating the IPv6 address space in the ranges of 2001::/16 to the five 5 registries (ARIN, RIPE, APNIC, LACNIC, and AfriNIC).
3.2.2 Reserved Addresses
The IETF reserves a part of the IPv6 address space for several kinds of uses, both present and future. Reserved addresses represent 1/256th of the all IPv6 address space. Some of the other types of IPv6 addresses come from this block.
3.2.3 Private Addresses
A block of IPv6 addresses is set aside for private addresses, just as is done in IPv4. These private addresses are local only to a specific link or site, and are therefore never routed outside of a specific company network. Private addresses have a first octet value of "FE" in hexadecimal notation, with the next hexadecimal digit being a value from 8 to F.
These addresses are further divided into two types, based upon their scope.
Site-local addresses, are addresses similar to the RFC 1918 Address Allocation for Private Internets in IPv4 today. The range of these addresses is an entire site or organization. However, the use of site-local addresses is tough and is being deprecated as of 2003 by RFC 3879. In hexadecimal, site-local addresses start with "FE" and then "C" to "F" for the third hexadecimal digit. So, these addresses begin with "FEC", "FED", "FEE", or "FEF".
Link-local addresses, are new to the concept of addressing with IP in the Network layer. These addresses have a smaller range than site-local addresses; they refer only to a particular physical link (physical network). Routers don't forward datagrams using link-local addresses at all, not even within the organization; they are only for local communication on a particular physical network segment. They are used for link communications such as automatic address configuration, neighbor discovery, and router discovery. Many IPv6 routing protocols also use link-local addresses. Link-local addresses begin with "FE" and then have a value from "8" to "B" for the third hexadecimal digit. So, these addresses start with "FE8", "FE9", "FEA", or "FEB".
3.2.4 Loopback Address
As in IPv4, a preparation has been made for a special loopback IPv6 address for testing; datagrams sent to this address "loop back" to the sending device. However, in IPv6 there is just one address, not a whole block, for this function. The loopback address which is normally expressed using zero compression as "::1".
3.2.5 Unspecified Address
In IPv6, the all-zeroes address (0:0:0:0:0:0:0:0) is named the "unspecified" address. It is typically used in the source field of a datagram that is sent by a device that searches to have its IP address configured. We can apply address compression to this address: the address becomes just "::".
3.3 IPv6 Address Management
IPv6 addresses use interface identifiers to identify interfaces on a link. Interface identifiers are needed to be unique on a specific link. Interface identifiers are always 64 bits and can be dynamically derived from a (MAC) address.
We can assign an IPv6 address ID statically or dynamically:
Static assignment using a manual interface ID
Static assignment using an EUI-64 interface ID
DHCP for IPv6 (DHCPv6)
3.3.1 Manual Interface ID Assignment
One way to statically assign an IPv6 address to a device is to manually assign both the prefix (network) and interface ID (host) portion of the IPv6 address. To configure an IPv6 address on a Cisco router interface, use the ipv6 address ipv6-address/prefix-length command in interface configuration mode. The following command shows the assignment of an IPv6 address to the interface of a Cisco router:
RouterX(config-if)#ipv6 address 2001:DB8:2222:7272::72/64
3.3.2 EUI-64 Interface ID Assignment
Another way to assign an IPv6 address is to configure the prefix (network) portion of the IPv6 address and derive the interface ID (host) portion from the MAC address of the device, which is known as the EUI-64 interface ID.
The EUI-64 standard explains how to stretch MAC addresses from 48 to 64 bits by inserting the 16-bit 0xFFFE in the middle at the 24th bit of the MAC address to create a 64-bit, unique interface identifier.
To configure an IPv6 address on a Cisco router interface and enable IPv6 processing using EUI-64 on that interface, use the ipv6 address ipv6-prefix/prefix-length eui-64 command in interface configuration mode. The following command shows the assignment of an EUI-64 address to the interface of a Cisco router:
RouterX(config-if)#ipv6 address 2001:DB8:2222:7272::/64 eui-64
3.3.3 Stateless Auto-configuration
Auto-configuration automatically configures the IPv6 address. In IPv6, it is assumed that non-PC devices, as well as computer terminals, will be connected to the network. The auto-configuration mechanism was introduced to enable plug-and-play networking of these devices to help reduce administration overhead.
3.3.4 DHCPv6 (Stateful)
DHCPv6 enables DHCP servers to pass configuration parameters, such as IPv6 network addresses, to IPv6 nodes. This protocol is a stateful counterpart to IPv6 stateless address auto-configuration (RFC 2462), and can be used separately or concurrently with IPv6 stateless address auto-configuration to obtain configuration parameters.
4. IPv6 Transition Strategies
The transition from IPv4 doesn't need upgrades on all nodes at the same time. Many transition mechanisms enable smooth integration of IPv4 and IPv6. Other mechanisms that provide IPv4 nodes to communicate with IPv6 nodes are available. Different situations demand different strategies. The figure illustrates the richness of available transition strategies.
The most common techniques to transition from IPv4 to IPv6 are:
Dual Stacking and
4.1 Dual Stacking
Dual stacking is an integration method in which a node has implementation and connectivity to both an IPv4 and IPv6 network. This is the recommended option and involves running IPv4 and IPv6 at the same time. Router and switches are configured to support both protocols, with IPv6 being the preferred protocol.
The second major transition technique is tunneling. There are several tunneling techniques available, including:
Manual IPv6-over-IPv4 tunneling - An IPv6 packet is encapsulated within the IPv4 protocol. This method requires dual-stack routers.
Dynamic 6to4 tunneling - It dynamically applies a valid, unique IPv6 prefix to each IPv6 island, which enables the fast preparation of IPv6 in a corporate network without address retrieval from the ISPs or registries.
5. Routing Considerations with IPv6
As IPv4 classless inter-domain routing (CIDR), IPv6 has longest prefix match routing. IPv6 uses modified versions of most of the common routing protocols to handle longer IPv6 addresses and different header structures.
Larger address spaces make room for large address allocations to ISPs and organizations. An ISP aggregates all of the prefixes of its customers into a single prefix and announces the single prefix to the IPv6 Internet. The increased address space is enough to allow organizations to define a single prefix for their entire network.
A brief review of how a router functions in a network helps illustrate how IPv6 affects routing. Conceptually, a router has three functional areas:
The control plane manages the interaction of the router with the other network elements, providing the information needed to make decisions and control the overall router operation. This plane runs processes such as routing protocols and network management
The data plane manages packet forwarding from one physical or logical interface to another. It involves different switching mechanisms such as process switching and Cisco Express Forwarding (CEF) on Cisco IOS software routers.
Enhanced services include advanced features applied when forwarding data, such as packet filtering, quality of service (QoS), encryption, translation, and accounting.
IPv6 introduces each of these functions with specific new challenges.
5.1 IPv6 Control Plane
Enabling IPv6 on a router starts its control plane operating processes specifically for IPv6. Protocol characteristics shape the performance of these processes and the amount of resources necessary to operate them:
IPv6 address size - For IPv6, the source and destination addresses require two cycles each-four cycles to process source and destination address information. As a result, routers relying exclusively on software processing are likely to perform slower than when in an IPv4 environment.
Multiple IPv6 node addresses - Because IPv6 nodes can use many IPv6 unicast addresses, memory consumption of the Neighbor Discovery cache may be affected.
IPv6 routing protocols - IPv6 routing protocols are almost same to their IPv4 counterparts, but since an IPv6 prefix is four times larger than an IPv4 prefix, routing updates have to carry more information.
Routing table Size -Increased IPv6 address space leads to larger networks and a much larger Internet. This means larger routing tables and higher memory requirements to support them.
5.2 IPv6 Data Plane
The data plane forwards IP packets based on the decisions made by the control plane. The forwarding engine parses the relevant IP packet information and does a lookup to match the parsed information against the forwarding policies defined by the control plane. IPv6 involves the performance of parsing and lookup functions:
Parsing IPv6 extension headers - Applications, including mobile IPv6, often use IPv6 address information in extension headers, thus increasing their size. These additional fields require additional processing
IPv6 address lookup - IPv6 performs a lookup on packets entering the router to find the correct output interface. In IPv6, the forwarding decision could conceivably need parsing a 128-bit address.
6. Configuring IPv6 Addresses
6.1 Enabling IPv6 on Cisco Routers
There are two basic steps to activate IPv6 on a router. First, we must activate IPv6 traffic-forwarding on the router, and then we must configure each interface that needs IPv6. By default, IPv6 traffic-forwarding is disabled on a Cisco router. To activate it between interfaces, we must configure the global command ipv6 unicast-routing.
The ipv6 address command can configure a global IPv6 address. The link-local address is automatically configured when an address is assigned to the interface. We must specify the entire 128-bit IPv6 address or specify to use the 64-bit prefix by using the eui-64 option.
6.2 IPv6 Address Configuration Example
We can completely specify the IPv6 address or compute the host identifier (rightmost 64 bits) from the EUI-64 identifier of the interface. For example, the IPv6 address of the interface is configured using the EUI-64 format. Alternatively, we can completely specify the entire IPv6 address to assign a router interface an address using the ipv6 address ipv6-address/prefix-length command in interface configuration mode. Configuring an IPv6 address on an interface automatically configures the link-local address for that interface.
6.3 Cisco IOS IPv6 Name Resolution
There are two ways to perform name resolution from the Cisco IOS process:
Define a static name for an IPv6 address using the ipv6 host name [port] ipv6-address1 [ipv6-address2...ipv6-address4] command. We can define up to four IPv6 addresses for one hostname. The port option refers to the Telnet port to be used for the associated host.
Specify the DNS server used by the router with the ip name-server address command. The address can be an IPv4 or IPv6 address. You can specify up to six DNS servers with this command.