IPv6 (Overview of IPv6)

IPv6 (Overview of IPv6)

In this "Learning with actual Cisco machine (CCNP) Part IV", we will introduce the configuration of a Cisco router using IPv6.

Before setting up, I will briefly explain the outline of IPv6.

Since IPv4 addresses consist of 32 bits, we can see that there are about 4.3 billion IP addresses.

 2 32  = 4,294,967,296

 This sounds like enough IP addresses, but given the world's population (6.6 billion as of January 2008), there's not even one IP address per person. Moreover, it is not possible to assign one IP address to one computer.

 In the first place, IPv4 addresses were roughly allocated in units of Class A, Class B, and Class C addresses at the beginning of allocation, so it seemed that IPv4 addresses would soon run out.

 As measures to prolong the life of IPv4, various schemes have been devised to conserve IP addresses, and unused IP addresses are collected and reused.

Even so, the exhaustion of IP addresses has become a concern.

Therefore, several methods have been devised to deal with this IP address exhaustion problem.

One of them is IPv6. Since IPv6 consists of 128 bits,

 2 128  = 3.4 × 10 38  pieces

To be exact


 Only about 4.3 billion x about 4.3 billion x about 4.3 billion x about 4.3 billion IP addresses can be secured. This number is effectively a large enough IP address space to be considered an infinite number of addresses. No need to worry about exhaustion.

 However, there are various obstacles to an immediate transition to IPv6. This is because network lines, service programs, and network terminals must support IPv6.

At present, it is difficult to say that IPv6 is being used because there is not much merit or necessity to migrate to IPv6.

 Whether or not IPv6 will become widespread is not yet known, but many vendors support IPv6. The transition from IPv4 to IPv6 is gradual, but it is certainly progressing.

As a network engineer, it is important to learn IPv6 in preparation for the transition from IPv4 to IPv6.

Benefits of IPv6

Benefits of IPv6 include:

  • 128-bit address space means no need to worry about running out of IP addresses
  • If IPv6 is introduced, address translation is basically unnecessary, and troubles caused by the NAT function are eliminated.
  • The IP address can also be automatically generated, reducing the hassle of setting an IP address.
  • Flexible to network configuration changes. Operations associated with address changes can be performed transparently to users
  • The IPv6 header is simpler than the IPv4 header, so it puts less load on routers and switches.
  • IPv4 uses broadcast addresses, but IPv6 uses multicast.
  • Since the addresses are strictly hierarchical, they can be aggregated efficiently.