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ICMPv6
Dell Networking OS supports ICMPv6.
ICMP for IPv6 combines the roles of ICMP, IGMP and ARP in IPv4. Similar to 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 4443.
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 ping and traceroute commands extend to support IPv6 addresses. These commands use ICMPv6 Type-2 messages.
Path MTU Discovery
Dell Networking OS supports IPv6 path maximum transmission unit (MTU) discovery.
The size of the packet that can be sent across each hop in the network path without being fragmented is called the path
maximum transmission unit (PMTU). The PMTU value might differ for the same route between two devices, mainly over a
public network, depending on the network load and speed, and it is not a consistent value. The MTU size can also be different
for various types of traffic sent from one host to the same endpoint. Path MTU discovery (PMTD) identifies the path MTU
value between the sender and the receiver, and uses the determined value to transmit the packets across the network. Path
MTU, in accordance with RFC 1981, defines the largest packet size that can traverse a transmission path without suffering
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
the processing efficiency because each packet carries more data while protocol overheads (for example, headers) or underlying
per-packet delays remain fixed.
Figure 59. Path MTU Discovery Process
IPv6 Neighbor Discovery
Dell Networking OS supports IPv6 neighbor discovery protocol (NDP).
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
IPv6 Routing
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