Link-State Advertisement Types For Ospfv3 - Cisco NCS 5500 Series Configuration Manuals

Link-State Advertisement Types for OSPFv3

• Router LSA (Type 1)—Describes the links that the router has within a single area, and the cost of each
• Network LSA (Type 2)—Describes the link state and cost information for all routers attached to a
• Summary LSA for ABRs (Type 3)—Advertises internal networks to routers in other areas (interarea
• Summary LSA for ASBRs (Type 4)—Advertises an ASBR and the cost to reach it. Routers that are
• Autonomous system external LSA (Type 5)—Redistributes routes from another autonomous system,
• Autonomous system external LSA (Type 7)—Provides for carrying external route information within
• Intra-area-prefix LSAs (Type 9)—A router can originate multiple intra-area-prefix LSAs for every router
• Area local scope (Type 10)—Opaque LSAs are not flooded past the borders of their associated area.
• Link-state (Type 11)—The LSA is flooded throughout the AS. The flooding scope of Type 11 LSAs are
Link-State Advertisement Types for OSPFv3
Each of the following LSA types has a different purpose:
• Router LSA (Type 1)—Describes the link state and costs of a the router link to the area. These LSAs are
Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 6.3.x
108
link. These LSAs are flooded within an area only. The LSA indicates if the router can compute paths
based on quality of service (QoS), whether it is an ABR or ASBR, and if it is one end of a virtual link.
Type 1 LSAs are also used to advertise stub networks.
multiaccess network segment. This LSA lists all the routers that have interfaces attached to the network
segment. It is the job of the designated router of a network segment to generate and track the contents
of this LSA.
routes). Type 3 LSAs may represent a single network or a set of networks aggregated into one prefix.
Only ABRs generate summary LSAs.
trying to reach an external network use these advertisements to determine the best path to the next hop.
ABRs generate Type 4 LSAs.
usually from a different routing protocol into OSPF.
an NSSA. Type 7 LSAs may be originated by and advertised throughout an NSSA. NSSAs do not receive
or originate Type 5 LSAs. Type 7 LSAs are advertised only within a single NSSA. They are not flooded
into the backbone area or into any other area by border routers.
or transit network, each with a unique link-state ID. The link-state ID for each intra-area-prefix LSA
describes its association to either the router LSA or network LSA and contains prefixes for stub and
transit networks.
equivalent to the flooding scope of AS-external (Type 5) LSAs. Similar to Type 5 LSAs, the LSA is
rejected if a Type 11 opaque LSA is received in a stub area from a neighboring router within the stub
area. Type 11 opaque LSAs have these attributes:
• LSAs are flooded throughout all transit areas.
• LSAs are not flooded into stub areas from the backbone.
• LSAs are not originated by routers into their connected stub areas.
flooded within an area only. The LSA indicates whether the router is an ABR or ASBR and if it is one
end of a virtual link. Type 1 LSAs are also used to advertise stub networks. In OSPFv3, these LSAs have
no address information and are network protocol independent. In OSPFv3, router interface information
may be spread across multiple router LSAs. Receivers must concatenate all router LSAs originated by
a given router before running the SPF calculation.
Implementing OSPF