• 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 MulticastListener 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 ICMPv6Type-2 messages.Path MTU DiscoveryPath MTU, in accordance with RFC 1981, defines the largest packet size that can traverse a transmission path without sufferingfragmentation. Path MTU for IPv6 uses ICMPv6 Type-2 messages to discover the largest MTU along the path from source todestination and avoid the need to fragment the packet.The recommended MTU for IPv6 is 1280. Greater MTU settings increase processing efficiency because each packet carries moredata while protocol overheads (for example, headers) or underlying per-packet delays remain fixed.Figure 42. Path MTU Discovery ProcessIPv6 Neighbor DiscoveryNDP 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 purgingcached values that become invalid.NOTE: If a neighboring node does not have an IPv6 address assigned, it must be manually pinged to allow the IPv6device to determine the relationship of the neighboring node.NOTE: To avoid problems with network discovery, Dell Networking recommends configuring the static route last orassigning an IPv6 address to the interface and assigning an address to the peer (the forwarding router’s address) lessthan 10 seconds apart.With ARP, each node broadcasts ARP requests on the entire link. This approach causes unnecessary processing by uninterestednodes. With NDP, each node sends a request only to the intended destination via a multicast address with the unicast address usedas the last 24 bits. Other hosts on the link do not participate in the process, greatly increasing network bandwidth efficiency.340 IPv6 Routing
