Random OSPF fun time.

Type 1 Router LSA

Type 2 Network LSA

Type 3 Summary LSA

Type 4 ASBR Summary LSA

Type 5 Autonomous system external LSA

Type 7 NSSA LSA

The type 2 LSA is used for DR/BDR to let them know which routers belong to the multi-access network.

The type 2 LSA is used to propagate the "tree" for each router in an area.

The type 2 LSA is only used in PPP-network types when DR and BDR is not used.

The type 2 LSA is used by the DR/BDR to tell the other routers in a segment which prefix they belong to and who the DR/BDR are.

Type 3 LSA is only propagated inside an area.

Type 3 LSA's are created from internal routers.

Type 3 LSA's needs an ASBR.

Type 3 LSA's needs an ABR.

Type 3 LSA's is only propagated between areas.

The router ID of the DR.

How to reach the ABR.

How to reach a specific area.

How to reach the ASBR.

ASBR sends out type 5 LSA to let other areas know how to reach it.

ASBR sends out type 5 LSA with summary information between areas.

ABR sends out type 5 LSA with external summary information between areas.

DR sends out type 5 LSA to propagate the multi-access segment with prefixes to other networks.

ASBR sends out type 5 LSA with summary information to other networks outside the OSPF-domain.

The type 7 LSA is used to propagate redistributed networks into Not-so-stubby-areas.

The type 7 LSA is used instead of type 3 LSA's that are blocked in totally stubby areas.

The type 7 LSA is exactly the same as the type 5 LSA.

The type 7 LSA carries information about external networks.

DR

ABR

ASBR

Backbone Router

Link LSA

Intra-area prefix LSA

Inter-area prefix LSA

Link-local LSA

The intra-area prefix LSA is the same as the type 1 and 2 LSA in OSPFv2.

The inter-area prefix LSA is the same as the type 1 and 2 LSA in OSPFv2.

The intra-area prefix is used to summarize networks between areas.

The inter-area prefix is used to summarize networks between areas.

Router LSA

Summary LSA

Network LSA

ASBR summary LSA

AS LSA

Type 7 LSA

MD5

Plain text

SHA

Timed based MD5

Shared secret

Area range

Summary-address

default-information originate

Auto-summary enable

Use the default-route command in router-configuration mode.

Create a static default-route and use the redistribute command.

Use the default-information originate command.

Use the default-information originate always command.

In the election of master and slave when database description packets are exchanged.

The calculation of shortest path.

The election of DR and BDR

In the creation of stub areas where priority 0 is used to flag an area as stub.

A database descriptor packet is another name for hello-packets which keeps the databases synchronized across all routers in an area.

It's used to compare the LSDB between routers in an area to see if more link-state Query packets need to be sent.

It describes the database of the router, what RID, prefix and if it's a DR or BDR.

it compares the LSDB of the routers participating in order to see what is missing in each database to get a fully synchronized topology of the area.