Reference Guide

IPv6 Routing | 407
Path MTU Discovery
IPv6 MTU Discovery is supported on platforms c e s z
Path MTU (Maximum Transmission Unit) 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 (headers, for example) or underlying per-packet
delays remain fixed.
Figure 19-2. MTU Discovery Path
IPv6 Neighbor Discovery
IPv6 NDP is supported on platforms c e s z
Router B
Router A
MTU = 1600 MTU = 1400 MTU = 1200
ICMPv6 (Type 2)
Use MTU = 1400
Packet (MTU = 1600)
Packet (MTU = 1400)
ICMPv6 (Type 2)
Use MTU = 1200
Packet (MTU = 1200)
Packet Received
Source
Destination