Users Guide
ICMPv6
ICMP for IPv6 combines the roles of ICMP, IGMP and ARP in IPv4.
Like IPv4, it provides functions for reporting delivery and forwarding errors, and provides a simple echo service for troubleshooting.
The Dell Networking OS implementation of ICMPv6 is based on RFC 2463.
Generally, ICMPv6 uses two message types:
• Error reporting messages indicate when the forwarding or delivery of the packet failed at the destination or intermediate node.
These messages include Destination Unreachable, Packet Too Big, Time Exceeded and Parameter Problem messages.
• Informational messages provide diagnostic functions and additional host functions, such as Neighbor Discovery and Multicast
Listener Discovery. These messages also include Echo Request and Echo Reply messages.
The Dell Networking OS ping and traceroute commands extend to support IPv6 addresses. These commands use ICMPv6
Type-2 messages.
Path MTU Discovery
Path MTU (Maximum Transmission Unit) denes the largest packet size that can traverse a transmission path without suering
fragmentation.
Path MTU for IPv6 uses ICMPv6 Type-2 messages to discover the largest MTU along the path from source to destination and avoid
the need to fragment the packet.
The recommended MTU for IPv6 is 1280. Greater MTU settings increase processing eciency because each packet carries more
data while protocol overheads (for example, headers) or underlying per-packet delays remain xed.
Figure 59. Path MTU Discovery Process
IPv6 Neighbor Discovery
NDP is a top-level protocol for neighbor discovery on an IPv6 network.
In lieu of address resolution protocol (ARP), NDP uses “Neighbor Solicitation” and “Neighbor Advertisement” ICMPv6 messages for
determining relationships between neighboring nodes. Using these messages, an IPv6 device learns the link-layer addresses for
neighbors known to reside on attached links, quickly purging cached values that become invalid.
IPv6 Routing
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