The ability to scale networks for future demands requires a limitless supply of IP addresses and improved mobility; IPv6 combines expanded addressing with a more efficient and feature-rich header to meet these demands. IPv6 satisfies the increasingly complex requirements of hierarchical addressing that IPv4 does not support.
The Cisco IOS supports IPv6 in Release 12.2(2)T and later. The main benefits of IPv6 include the following:
■ Larger address space: IPv6 addresses are 128 bits, compared to IPv4's 32 bits. This larger addressing space allows more support for addressing hierarchy levels, a much greater number of addressable nodes, and simpler autoconfiguration of addresses.
■ Globally unique IP addresses: Every node can have a unique global IPv6 address, which eliminates the need for NAT.
■ Site multihoming: IPv6 allows hosts to have multiple IPv6 addresses and allows networks to have multiple IPv6 prefixes. Consequently, sites can have connections to multiple ISPs without breaking the global routing table.
■ Header format efficiency: A simplified header with a fixed header size makes processing more efficient.
■ Improved privacy and security: IPsec is the IETF standard for IP network security, available for both IPv4 and IPv6. Although the functions are essentially identical in both environments, IPsec is mandatory in IPv6. IPv6 also has optional security headers.
■ Flow labeling capability: A new capability enables the labeling of packets belonging to particular traffic flows for which the sender requests special handling, such as nondefault quality of service (QoS) or real-time service.
■ Increased mobility and multicast capabilities: Mobile IPv6 allows an IPv6 node to change its location on an IPv6 network and still maintain its existing connections. With Mobile IPv6, the mobile node is always reachable through one permanent address. A connection is established with a specific permanent address assigned to the mobile node, and the node remains connected no matter how many times it changes locations and addresses.
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