Information Technology Reference
In-Depth Information
The following sections cover topics that you need to master for the CCDA exam. The sec-
tion “IPv6 Header” covers each field of the IPv6 header, which helps you understand the
protocol. The section “IPv6 Address Representation” covers the hexadecimal representa-
tion of IPv6 addresses and the compressed representation. The section “IPv6 Address
Ty pes” covers unic ast, multic ast, and anyc ast IP v6 addres ses, spec ial addres s t y pes, and
the current allocations of IPv6 addresses.
The section “IPv6 Mechanisms” covers Internet Control Message Protocol Version 6
(ICMPv6), ND, address assignment and resolution, and introduces IPv6 routing protocols.
The section “IPv4 to IPv6 Transition Strategies and Deployments” covers dual-stack back-
bones, IPv6 over IPv4 tunnels, dual-stack hosts, and Network Address Translation-Protocol
Tran slat ion (NAT-P T ).
Yo u s h o u l d b e c o m e f a m i l i a r a t a h i g h l e v e l w i t h I P v 6 s p e c i f i c a t i o n s , a d d r e s s i n g , a n d d e -
sign. The driving motivation for the adoption of a new version of IP is the limitation im-
posed by the 32-bit address field in IPv4. In the 1990s, there was concern that the IP
address space would be depleted soon. Although classless interdomain routing (CIDR) and
NAT have slowed down the deployment of IP v6, its standards and deployments are be-
coming mature. IPv6 is playing a significant role in the deployment of IP services for wire-
less phones. Some countries such as Japan directed IPv6 compatibility back in 2005.
Other countries, such as China, France, and Korea, have been implementing IPv6. The
2008 Summer Olympics was accessible from the IPv6 Internet. The U.S. federal govern-
ment had mandated all agencies to support IPv6 by mid 2008. Operating systems such as
Windows 7, Vista, Linux, Mac OS, and others all support IPv6. Google and Facebook are
also accessible in the IPv6 Internet.
The IPv6 specification provides 128 bits for addressing, a significant increase from 32
bits. The overall specification of IPv6 is in RFC 2460. Other RFCs describing IPv6 specifi-
cations are 4921, 3513, 3587, 3879, 2373, 2374, 2461, 1886, and 1981.
IPv6 includes the following enhancements over IPv4:
Larger address space:
IPv6 uses 128-bit addresses rather than the 32-bit ad-
dresses in IPv4. This supports more address hierarchy levels and uses simpler address
autoconfiguration.
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Key
To p i c
Globally unique IP addresses:
The additional address space allows each node to
have a unique address and eliminate the need for NAT.
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Header format efficiency:
The IPv6 header length is fixed, lowering header pro-
cessing time and thus allowing vendors to improve packet switching efficiency.
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Improved option mechanism:
IPv6 options are placed in separate optional headers
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headers are not required.
