Windows 7 on the 2009 A+ Exams

IPv6 Addresses

Many enterprise organizations are converting from IPv4 to IPv6. In addition, a portion of the Internet has already converted to IPv6. As a technician in an enterprise, you need to be aware of how IP addresses using IPv6 are read and address conventions.

An IP address is a series of numbers that uniquely identifies a node on a TCP/IP network including the Internet and an intranet. The standard that determines an IP address with 32 bits is called the IPv4 (Internet Protocol version 4) standard. Partly because of potential shortages of IP addresses and partly because of the need for increased security on the Internet, the IPv6 (IP version 6) standard has been introduced. IPv6 uses 128 bits for an IP address. All versions of Windows since Windows XP with Service Pack 2 support IPv6.

Here are a few facts about writing and displaying IPv6 addresses:

• 
  An IPv6 address has 128 bits that are written as 8 blocks of hexadecimal numbers separated by colons, like this: 2001:0000:0B80:0000:0000:00D3:9C5A:00CC.
  
• 
  Each block is 16 bits. For example, the first block in the address above is 2001 in hex, which can be written as 0010 0000 0000 0001 in binary.
  
• 
  Leading zeros in a 4-character hex block can be eliminated. For example the IP address above can be written as 2001:0000:B80:0000:0000:D3:9C5A:CC.
  
• 
  If blocks contain all zeroes, they can be written as double colons (::). The IP address above can be written two ways:
  
  • 
    2001::B80:0000:0000:D3:9C5A:CC
    
  • 
    2001:0000:B80::D3:9C5A:CC
    

Here are a few terms used in the IPv6 standards:

• 
  A link, sometimes called the local link, is a local area network (LAN) or wide area network (WAN) bounded by routers.
  
• 
  A subnet is one or more links that have the same 64 bits in the first part of the IP address (called the prefix). Recall that when using IPv4, the subnet could be identified by any number of bits at the beginning of the IP address. Using IPv6, the subnet is almost always identified using the first 64 bits.
  

To learn more about subnets and subnet masks see Pages 881 through 882 in Chapter 17 of A+ Guide to Managing and Maintaining Your PC or Pages 389 through 390 in Chapter 8 of A+ Guide to Software.

• 
  Neighbors are two or more nodes on the same link.
  
• 
  An interface is a node’s attachment to a link. The attachment can be a physical attachment using a network adapter or wireless connection or a logical attachment such as when a tunneling protocol is used to connect the node to a server.
  
• 
  The last 64 bits or 4 blocks of an IP address identify the interface and are called the interface ID or interface identifier. These 64 bits uniquely identify an interface on the local link.
  

• 
  Using a unicast address, packets are delivered to a single node on a network.
  
• 
  Using a multicast address, packets are delivered to all nodes on a network.
  
• 
  An anycast address is used by routers. The address identifies multiple destinations and packets are delivered to the closest destination.
  

• 
  A global unicast address can be routed on the Internet. These addresses are similar to IPv4 public IP addresses.
  
• 
  A link-local unicast address can be used for communicating with nodes in the same link. These addresses are similar to IPv4 private IP addresses and are sometimes called link-local addresses.
  
• 
  A unique local unicast address can work on multiple links within the same organization. The address is a hybrid between a global unicast address that works on the Internet and a link-local unicast address that works on only one link.