70
Figure 33
Network LSA format
Major fields of the Network LSA are as follows:
•
Link state ID: The interface address of the DR.
•
Network mask: The mask of the network (a broadcast or NBMA network).
•
Attached router: The IDs of the routers, which are adjacent to the DR, including the DR itself.
3.
Summary LSA
Network summary LSAs (Type-3 LSAs) and ASBR summary LSAs (Type-4 LSAs) are originated by ABRs.
Except for the Link state ID field, the formats of Type 3 and 4 summary-LSAs are identical.
Figure 34
Summary LSA format
Major fields of the Summary LSA are as follows:
•
Link state ID: For a Type-3 LSA, it is an IP address outside the area. For a type 4 LSA, it is the router
ID of an ASBR outside the area.
•
Network mask: The network mask for the type 3 LSA. It is set to 0.0.0.0 for the Type-4 LSA.
•
Metric: The metric to the destination.
NOTE:
A Type-3 LSA can be used to advertise a default route if the link state ID and network mask are set to
0.0.0.0.
4.
AS external LSA
