Multicast OSPF LSA (Type 6) on Cisco router

Cisco routers do not support LSA Type 6 Multicast OSPF (MOSPF), and they generate syslog messages if they receive such packets. If the router is receiving many MOSPF packets, you might want to configure the router to ignore the packets and thus prevent a large number of syslog messages.


Commands:
#Router ospf 0.0.0.1
#ignore lsa mospf

What Do We Mean by Link-States?

What Do We Mean by Link-States?

OSPF is a link-state protocol. We could think of a link as being an interface on the router. The state of the link is a description of that interface and of its relationship to its neighboring routers. A description of the interface would include, for example, the IP address of the interface, the mask, the type of network it is connected to, the routers connected to that network and so on. The collection of all these link-states would form a link-state database.

OSPF LSA in Details

Somedays before (last year), I have published a post about the OSPF LSAs types and definitions. Today I am going to share some more details about the SLAs as which router will generate the which LSAs:

1. 

SLA Name: Router LSA 

Link-State ID: Originating router ID of the router

Generated By: Router LSAs are generated by every router. 

2. 

SLA Name: Network LSA 

Link-State ID: Interface IP address of the DR

Generated By: Network LSAs are generated by the DR on a multi-access segment. They are the representation of the multi-access segment and all the routers attached to the segment. Segments that do not have a DR, such as point-to-point, will not have a network LSA.

3.

SLA Name: Network summary LSA

Link-State ID: Destination network number

Generated By: Network summary LSAs are generated by ABRs. 

4.

SLA Name: ASBR summary LSA

Link-State ID: Router ID of AS boundary router

Generated By: ASBR summary LSAs are also generated by the ABR. This LSA describes the location of an ASBR, not a network. 

5. 

SLA Name: AS external LSA

Link-State ID: External network number

Generated By: Autonomous System (AS) External LSAs are originated by the ASBRs and describe a network outside of the AS.

7. 

SLA Name: NSSA external LSA
Link-State ID: External network number
Generated By: Not-So-Stubby Area (NSSA) external LSAs are originated by the ASBR within the NSSA. These types of LSAs are flooded only throughout the NSSA.

I hope it will very helpful for you!

OSPF LSA Types

OSPF uses a LSDB (link state database) and fills this with LSAs (link state advertisement).

Here Some details about all SLA types:-

• LSA Type 1 (Router LSA)

Router Link State Advertisements Type 1 are generated by every router for each link that belongs to an area. They are flooded only inside of area to which they belong. Link ID of this LSA is the Router ID of the router that generated it.

• LSA Type 2 (Network LSA)

Generated by Designated Router (DR) for multiaccess networks and describe the routers that are connected to that segment. They are sent inside the area to which the network segment belong.

• LSA Type 3 (Summary LSA)

Type 3 LSAs are generated by Area Border Routers (ABRs). In type 3 LSAs are advertised networks from an area to the rest of the areas in AS. Advertised networks in Type 4 LSA can be summarized or not. The link-state id used by this LSA is the network number advertised.

• LSA Type 4 (ASBR Summary LSA)

Generated by ABRs, this type of LSA contain routes to ASBRs. Link id used is router ID of the ASBR described. Are not flooded in stub areas.

• LSA Type 5 (External LSA)

Autonomous system external LSAs are generated by ASBRs and contain routes to networks that are external to current AS. Link-state ID is network number advertised in LSA. Type 5 LSAs are not flooded inside any stub areas.

• LSA Type 6 (Multicast LSA)

This type of LSA is used for multicast applications. Not supported on Cisco.

• LSA Type 7 (NSSA External LSA)

Type 7 LSA allow injection of external routes through Not-so-Stubby-Areas (NSSA). Generally external routes are advertised by type 5 LSA but they are not allowed inside any stub area.
 Type 7 LSA is generated by NSSA ASBR and is translated into type 5 LSA as it leaves the area by NSSA ABR, which is then propagated throughout the network as type 5 LSA.

• LSA Type 8 (External LSA for BGP)

Used to work with BGP.

• LSA Type 9,10,11 (Opaque LSAs)