IPv6 Addressing

IPv6 Overview

Currently, the last of the IPv4 address blocks has been distributed and the internet is being slowly transitioned to IPv6. As a consequence, both professional networkers and networking students alike need to learn the details of IPv6 and begin configuring IPv6 enabled networks. In fact, there currently is a second internet, an  IPv6 Internet, where IPv6 is being implemented by governments, ISPs, and large organizations like Google.

 IPv6 Fundamentals LiveLessons: A Straightforward Approach to Understanding IPv6

What are the benefits of IPv6? First off, the IPv6 address space is a LOT longer than the IPv4 address space which means it will not run out of addresses like it did with IPv4. Here are some of the other IPv6 benefits:

• A simplified network prefix with no subnet mask required
• No reserved network addresses and broadcast addresses like with IPv4
• No DHCP server is required because hosts can autoconfigure their IPv6 and gateway address by soliciting network information from the router through router solicitation (RS) and router advertisement (RA)
• IPv6 has a simplified header improving efficiency and forwarding performance
• IPv6 has support for security platforms like IPsec and mobile IP
• IPv6 improves network performance by eliminating excessive network broadcasts by replacing broadcast addressing with more efficient multicast addresses

If you want an incredible resource for learning IPv6 visit Rick Graziani’s IPv6 resource page everything I know about IPv6 I have learned from Rick.

IPv6 Fundamentals: A Straightforward Approach to Understanding IPv6

IPv6 Address Structure

The IPv6 address is 128 bits long, written in hexadecimal notation separated by colons every 16 bits (see below). For the sake of abbreviation and simplification, leading zeros can be omitted and multiple 16bit sections of zeros can be replaced with a double colon (::). The double colon substitution can only be used once in the address.

Complete 128bit IPv6 address:  2001:0DB8:0001:2F00:0000:0000:0000:0000 /64
Abbreviated IPv6 address:  2001:DB8:1:2F00:: /64

The slash notation at the end of the address, in decimal format, identifies the number of bits, counting from left to right, that make up network prefix in the address. In the example below, the IPv6 address has /64 at the end, so the first 64 bits, the network prefix, is highlighted in red (see below). Remember that each hexadecimal character is base16, which is equivalent to 4 bits.

The network portion of the address and prefix highlighted in red: 2001:0DB8:0001:2F00:0000:0000:0000:0000 /64


Video Tutorial

In this video, I demonstrate IPv6 inter-network communication. IPv6 routing is configured on an 1841 Cisco router and also on two host PCs.

Author: Dan

Dan teaches computer networking and security classes at Central Oregon Community College.

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