Network setup - How to - Routers - Cisco - Linux

IPv6 is the new version of the IP protocol. IPv6 has been designed by the IETF to gradually replace IPv4 protocol. In this version, some features have remained above protocol, and have removed some functions that are used infrequently.

Main features of IPv6

*Larger address space. The IP address size changes from 32 bits to 128 bits, to support: more levels of addressing hierarchy and more addressable nodes.

*Header Format Simplification. Some IPv4 header fields are removed or made optional

*Efficient and extensible IP packets, with no fragmentation at routers, aligned to 64 bits and a fixed-length header, simplest, which speeds up its processing by the router.

*Possibility packet payload (data) greater than 65,355 bytes.

*Core security protocol (IPsec). IPsec support is a requirement of IPv6.

*Capacity flow labels. IPv6 can be used by a source node for tagging packets belonging to a particular traffic flow, which require special handling by the IPv6 routers, such as non-QoS default or real time services. For example video conferencing.

*Autoconfiguration: address autoconfiguration is simpler, the upper 64 bits are set by a message from the router (Router Advertisement) and the lower 64 bits are obtained with the MAC address (EUI-64 format). In this case, the length of the subnet prefix is 64, so no need to worry more about the network mask.

*Renumbering and "multihoming": facilitating change service provider.

*Mobility characteristics, the possibility that a node keeps the same IP address, despite their mobility.

*More efficient routing backbone network because the addressing hierarchy based on aggregation.

*Quality of Service (QoS) and Class of Service (CoS).

*Authentication and Privacy Capabilities


IPv6 Addressing

The addresses are 128 bits and identify individual interfaces, or sets of interfaces. As in IPv4, the nodes are assigned to interfaces.

They are classified into three types:

• Unicast: identify a single interface. A packet sent to a unicast address is delivered only to the interface identified by that address. [RFC 2373] [RFC 2374]
• Anycast: identify a set of interfaces. A packet sent to an anycast address will be delivered to any of the interfaces identified by the address of the set to which belongs the anycast address. [RFC 2526]
• Multicast: identify a group of interfaces. When a packet is sent to a multicast address is delivered to all interfaces identified by that address group.

In IPv6, there are no broadcast addresses, its functionality has been improved by multicast addresses. [RFC 2375]


Representation of IPv6 Addresses

There are three ways of representing IPv6 addresses as text strings.

• x:x:x:x:x:x:x:x where each x is a hexadecimal value of 16 bits, each of the 8 fields that define the direction. It is not necessary to write the leading zeros in each field, but at least there should be a number in each field.

Examples:

FEDC:BA98:7654:3210:FEDC:BA98:7654:3210
1080:0:0:0:8:800:200C:417A

• As is common with addressing schemes using long strings of bits to zero, the possibility to use to represent syntactically ::. Use :: indicates one or more groups of 16 bits of zeros. This symbol may appear only once in each direction.

Examples:
1080:0:0:0:8:800:200C:417A unicast address
FF01:0:0:0:0:0:0:101 multicast address
0:0:0:0:0:0:0:1 loopback address
0:0:0:0:0:0:0:0 unspecified addresses

may be represented as:
1080::8:800:200C:417A unicast address
FF01::101 multicast address
::1 loopback address
:: unspecified addresses

For scenarios with IPv4 and IPv6 nodes can use the following syntax:

x:x:x:x:x:x:d.d.d.d, where x represent hexadecimal values ​​of the six most significant parts (16 bits each) that make up the direction and d are decimal values ​​of the four least significant parts (of 8 bits each), standard representation IPv4 address format.

Examples:
0:0:0:0:0:0:13.1.68.3
0:0:0:0:0:FFFF:129.144.52.38

or in compressed form:
::13.1.68.3
::FFFF:129.144.52.38


Representing address prefixes

Identifiers prefixes subnets, routers and IPv6 address ranges are expressed in the same way as in CIDR notation used in IPv4.

An IPv6 address prefix is represented by the following notation:

address-ipv6/length-prefix, which

address-ipv6: is an IPv6 address in either of the above notations.
length-prefix: is a decimal value specifying how many of the most significant bits represent the address prefix.


Global Unicast Address

Format Global unicast addresses


Global routing prefix: a prefix assigned to a site, generally is structured hierarchically by the RIRs and ISPs.
Subnet Identifier: the identifier of a subnet within a site. It is designed for site managers as hierarchically structured
Interface identifier: the identifier of an interface. In all unicast addresses, except those that start with binary value 000, the interface identifier must be 64 bits and be constructed in Modified EUI-64 format.

The format for this case is as follows:



Calculation of IPv6 address using the MAC

A MAC address set manually or by software should not be used to derive from it the interface identifier, but if no other formula, your property should be reflected in the value of bit U/L.


DNS

The current storage Internet addresses in the Domain Name System (DNS) of IPv4 can not be easily extended to support 128-bit IPv6 addresses. This is because applications assume that address queries return only IPv4 addresses are 32-bit.

In order to store IPv6 addresses defined the following extensions (see RFC 3596)

• A new type of record, the AAAA record. Used to store IPv6 addresses, because the extensions are designed to be compatible with existing DNS implementations.
• A new domain to support lookups based on IPv6 addresses. This domain is IP6.ARPA.
• Redefining existing queries that locate IPv4 addresses. For IPv6 addresses can also process.

The changes are designed to be compatible with existing software. Maintain support IPv4 addresses.