3Com Switch 4800G 24-Port Configuration Manual page 289

Figure 89 Network LSA format
0 7
LS age
LS checksum
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
Summary LSA
■
Network summary LSAs (Type-3 LSAs) and ASBR summary LSAs (Type-4 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 90 Summary LSA format
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LS age
LS checksum
0
TOS
Major fields:
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; set to 0.0.0.0 for the
■
Type-4 LSA
metric: The metric to the destination
■
15
Options
Linke state ID
Advertising Router
LS sequence number
Network mask
Attached router
...
15
Options
Linke state ID
Advertising Router
LS sequence number
Network mask
metric
TOS metric
...
Introduction to OSPF 289
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