3Com Switch 8800 Advanced Software V5 Configuration Guide

Introduction to OSPF 317
Figure 99 Network LSA format
Major fields:
■ 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 (Type3 LSAs) and ASBR summary LSAs (type4 LSAs) are
originated by ABRs. Other than the difference in the Link State ID field, the format
of type 3 and 4 summary-LSAs is identical.
Figure 100 Summary LSA format
Major fields:
■ Link State ID: For a Type3 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; set to 0.0.0.0 for the
type4 LSA
■ metric: The metric to the destination
Network mask
...
Attached router
LS age
Linke state ID
Advertising Router
Options 2
LS sequence number
LS checksum Length
0715 31
Network mask
...
TOS
LS age
Linke state ID
Advertising Router
Options 3or4
LS sequence number
LS checksum Length
TOS metric
0 metric
0 7 15 31