3Com 4800G Series, Configuration Manual

Page: 444 / 1246

444 C
HAPTER
34: IP
V
6 OSPF
V
3 C
ONFIGURATION
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
flooding scope. It was introduced because Router-LSAs and Network-LSAs
contain no address information now.
Timers of OSPFv3 Timers in OSPFv3 include:
■
OSPFv3 packet timer
■
LSA delay timer
■
SPF timer
OSPFv3 packet timer
Hello packets are sent periodically between neighboring routers for finding and
maintaining neighbor relationships, or for DR/BDR election. The hello interval must
be identical on neighboring interfaces. The smaller the hello interval, the faster the
network convergence speed and the bigger the network load.