21IPv6 RoutingInternet protocol version 6 (IPv6) routing is supported on Dell Networking OS.NOTE: The IPv6 basic commands are supported on all platforms. However, not all features are supported on all platforms,nor for all releases. To determine the Dell Networking Operating System (OS) version supporting which features andplatforms, refer to Implementing IPv6 with Dell Networking OS.IPv6 is the successor to IPv4. Due to the rapid growth in internet users and IP addresses, IPv4 is reaching its maximum usage. IPv6will eventually replace IPv4 usage to allow for the constant expansion.This chapter provides a brief description of the differences between IPv4 and IPv6, and the Dell Networking support of IPv6. Thischapter is not intended to be a comprehensive description of IPv6.Protocol OverviewIPv6 is an evolution of IPv4. IPv6 is generally installed as an upgrade in devices and operating systems. Most new devices andoperating systems support both IPv4 and IPv6.Some key changes in IPv6 are:• Extended address space• Stateless autoconfiguration• Header format simplification• Improved support for options and extensionsExtended Address SpaceThe address format is extended from 32 bits to 128 bits. This not only provides room for all anticipated needs, it allows for the use ofa hierarchical address space structure to optimize global addressing.Stateless AutoconfigurationWhen a booting device comes up in IPv6 and asks for its network prefix, the device can get the prefix (or prefixes) from an IPv6router on its link. It can then autoconfigure one or more global IPv6 addresses by using either the MAC address or a private randomnumber to build its unique IPv6 address.Stateless autoconfiguration uses three mechanisms for IPv6 address configuration:• Prefix Advertisement — Routers use “Router Advertisement” messages to announce the network prefix. Hosts then use theirinterface-identifier MAC address to generate their own valid IPv6 address.• Duplicate Address Detection (DAD) — Before configuring its IPv6 address, an IPv6 host node device checks whether thataddress is used anywhere on the network using this mechanism.• Prefix Renumbering — Useful in transparent renumbering of hosts in the network when an organization changes its serviceprovider.NOTE: As an alternative to stateless autoconfiguration, network hosts can obtain their IPv6 addresses using the dynamichost control protocol (DHCP) servers via stateful auto-configuration.NOTE: Dell Networking OS provides the flexibility to add prefixes on Router Advertisements (RA) to advertise responsesto Router Solicitations (RS). By default, RA response messages are sent when an RS message is received.IPv6 Routing 333
