68
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.
•
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.
•
AS external LSA