3Com Switch 8800 Advanced Software V5 Configuration Guide

354 CHAPTER 31: IPV6 OSPFV3 CONFIGURATION
The five packets have the same packet header, which different from the OSPFv2
packet header is only 16 bytes in length, has no authentication field, but is added
with an Instance ID field to support multi-instance per link.
Figure 108 gives the OSPFv3 packet header.
Figure 108 OSPFv3 packet header
Major fields:
■ Version #: Version of OSPF, which is 3 for OSPFv3.
■ Type: Type of OSPF packet, from 1 to 5 are hello, DD, LSR, LSU, and LSAck
respectively.
■ Packet Length: Packet length in bytes, including header.
■ Instance ID: Instance ID for a link.
■ 0: Reserved, which must be 0.
OSPFv3 LSA Types OSPFv3 sends routing information in LSAs, which as defined in RFC2740 have the
following types:
■ Router-LSAs: Originated by all routers. This LSA describes the collected states of
the router’s interfaces to an area. Flooded throughout a single area only.
■ Network-LSAs: Originated for broadcast and NBMA networks by the
Designated Router. This LSA contains the list of routers connected to the
network. Flooded throughout a single area only.
■ Inter-Area-Prefix-LSAs: Similar to Type 3 LSA of OSPFv2, originated by ABRs
(Area Border Routers), and flooded throughout the LSA’s associated area. Each
Inter-Area-Prefix-LSA describes a route with IPv6 address prefix to a destination
outside the area, yet still inside the AS (an inter-area route).
■ Inter-Area-Router-LSAs: Similar to Type 4 LSA of OSPFv2, originated by ABRs
and flooded throughout the LSA’s associated area. Each Inter-Area-Router-LSA
describes a route to ASBR (Autonomous System Boundary Router).
■ AS-external-LSAs: Originated by ASBRs, and flooded throughout the AS
(except Stub and NSSA areas). Each AS-external-LSA describes a route to
another Autonomous System. A default route can be described by an AS
external LSA.
■ Link-LSAs: A router originates a separate Link-LSA for each attached link.
Link-LSAs have link-local flooding scope. Each Link-LSA describes the IPv6
address prefix of the link and Link-local address of the router.
■ Intra-Area-Prefix-LSAs: Each Intra-Area-Prefix-LSA contains IPv6 prefix
information on a router, stub area or transit area information, and has area
Packet length
Router ID
Area ID
TypeVersion #
Checksum 0Instance ID
015 31