Users Guide

• Prefix Advertisement — Routers use “Router Advertisement” messages to announce the network prefix.
Hosts then use their interface-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 that address 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 service provider.
NOTE: As an alternative to stateless autoconfiguration, network hosts can obtain their IPv6 addresses
using the dynamic host control protocol (DHCP) servers via stateful auto-configuration.
NOTE: Dell Networking OS provides the flexibility to add prefixes on Router Advertisements (RA) to
advertise responses to Router Solicitations (RS). By default, RA response messages are sent when an RS
message is received. Enable the RA response messages with the ipv6 nd prefix default command
in INTERFACE mode.
Dell Networking OS manipulation of IPv6 stateless autoconfiguration supports the router side only. Neighbor
discovery (ND) messages are advertised so the neighbor can use this information to auto-configure its
address. However, received ND messages are not used to create an IPv6 address.
The router redirect functionality in the neighbor discovery protocol (NDP) is similar to IPv4 router redirect
messages. NDP uses ICMPv6 redirect messages (Type 137) to inform nodes that a better router exists on the
link.
IPv6 Headers
The IPv6 header has a fixed length of 40 bytes. This fixed length provides 16 bytes each for source and
destination information and eight bytes for general header information.
The IPv6 header includes the following fields:
• Version (4 bits)
• Traffic Class (8 bits)
• Payload Length (16 bits)
• Next Header (8 bits)
• Hop Limit (8 bits)
• Source Address (128 bits)
• Destination Address (128 bits)
IPv6 provides for extension headers. Extension headers are used only if necessary. There can be no extension
headers, one extension header or more than one extension header in an IPv6 packet. Extension headers are
defined in the Next Header field of the preceding IPv6 header.
IPv6 Routing 541