Users Guide

IPv6 Headers
The IPv6 header has a fixed length of 40 bytes. This fixed length provides 16 bytes each for source and
destination information and 8 bytes for general header information.
The IPv6 header includes the following fields:
• Version (4 bits)
• Traffic Class (8 bits)
• Flow Label (20 bits)
• Payload Length (16 bits)
• Next Header (8 bits)
• Hop Limit (8 bits)
• Source Address (128 bits)
• Destination Address (128 bits)
IPv6 provides for extension headers. Extension headers are used only if necessary. There can be no extension
headers, one extension header or more than one extension header in an IPv6 packet. Extension headers are
defined in the Next Header field of the preceding IPv6 header.
Longest Prefix Match (LPM) Table and IPv6 /65
– /128 support
Two partitions are available.
• Partition I with IPv6 /65 – /128 route prefix. Doesn’t support IPv4 entries in the current release.
• Partition II with IPv6 0/0 – /64 route prefix and IPv4 0/0 -0/32 route prefix entries.
• Number of entries in Partition II will be reduced based on the number of entries configured in Partition I.
• Partitioning will be applied well before the system initialization. This will be done using the NVRAM.
• Dell Networking OS provides CLI for enabling the partition. Configuration will be stored in NVRAM when
the operator saves the configuration.
• Partition will take effect only after the switch reboot. During the reboot Dell Networking OS reads the
partition configuration from NVRAM and uses the same for partitioning the LPM.
• A command has been introduced to partition the LPM to support provisioning of IPv6 /65 to /128 route
prefixes.
To support /65 – /128 IPv6 route prefix entries, Dell Networking OS needs to be programmed with /65 - /128
bit IPv6 support. The number of entries as well needs to be explicitly programmed. This number can be1K, 2K,
or 3K granularity.
On the system, for IPv6 /65 to /128 will consume the same storage banks which is used by the L3_DEFIP
table. Once the IPv6 128 bit is enabled, number of entries in L3_DEFIP will be reduced.
LPM partitioning will take effect after reboot of the box. This is because the SDK does the LPM partitioning
during the chip initialization.
IPv6 Routing 477