Reference Guide

partition. The valid values are 1024, 2048 or 3072 prefixes. You must save the configuration and reload the switch for the
change to take effect.
● The number of entries in Partition II is reduced as the number of entries in Partition I increases.
● To disable LPM CAM partitioning and return the number of the IPv6 /65-/128 route prefixes stored in Partition 1 to 0, enter
the no cam-ipv6 extended-prefix command.
● Use the show cam-ipv6 extended-prefix command to display the currently configured number of IPv6 /65-/128
prefixes that can be stored in LPM CAM Partition 1 and the number that are supported after the next switch reboot.
ICMPv6
ICMP for IPv6 (ICMPv6) 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 implementation of ICMPv6 is based
on RFC 4443.
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
IPv6 path maximum transmission unit (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 processing efficiency because each packet carries
more data while protocol overheads (for example, headers) or underlying per-packet delays remain fixed.
Figure 50. Path MTU Discovery Process
IPv6 Routing
389