Users Guide

recommended MTU for IPv6 is 1280. Greater MTU settings increase the processing efficiency because each packet carries more
data while protocol overheads (for example, headers) or underlying per-packet delays remain fixed.
Figure 55. Path MTU discovery process
Stateless Autoconfiguration
When a booting device comes up in IPv6 and asks for its network prefix, the device can get the prefix (or prefixes) from an IPv6
router on its link. It can then autoconfigure one or more global IPv6 addresses by using either the MAC address or a private
random number 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
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 EMC 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.
Dell EMC 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.
NOTE:
Inconsistencies in router advertisement values between routers are logged per RFC 4861. The values checked for
consistency include:
● Cur Hop limit
● M and O flags
● Reachable time
● Retrans timer
● MTU options
● Preferred and valid lifetime values for the same prefix
Only management ports support stateless auto-configuration as a host.
IPv6 Routing 423