Concept Guide
The platforms uses only IPv6 /0 – 0/64 prex route entries. Support for /0 – /128 IPv6 prex route entries is available, although they are
not utilized. A total of eight pools or regions are present with each region containing 1024 210-bit entries (supports up to 0/64 prex). To
support up to /128 prexes, you must use 2 banks (410-bit entries). It is necessary to partition the LPM.
The optimized booting functionality does not use Openow and therefore SDN support is not available. LPM partitioning might have a slight
impact on the number of SDN-programmed L3 entries because the LPM space becomes reduced.
IPv6 Header Fields
The 40 bytes of the IPv6 header are ordered, as shown in the following illustration.
Figure 60. IPv6 Header Fields
Version (4 bits)
The Version eld always contains the number 6, referring to the packet’s IP version.
Trac Class (8 bits)
The Trac Class eld deals with any data that needs special handling. These bits dene the packet priority and are dened by the packet
Source. Sending and forwarding routers use this eld to identify dierent IPv6 classes and priorities. Routers understand the priority
settings and handle them appropriately during conditions of congestion.
Flow Label (20 bits)
The Flow Label eld identies packets requiring special treatment in order to manage real-time data trac.
The sending router can label sequences of IPv6 packets so that forwarding routers can process packets within the same ow without
needing to reprocess each packet’s header separately.
NOTE
: All packets in the ow must have the same source and destination addresses.
Payload Length (16 bits)
The Payload Length eld species the packet payload. This is the length of the data following the IPv6 header. IPv6 Payload Length only
includes the data following the header, not the header itself.
The Payload Length limit of 2 bytes requires that the maximum packet payload be 64 KB. However, the Jumbogram option type Extension
header supports larger packet sizes when required.
IPv6 Routing
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