What is LSA in Cisco?
The link-state advertisement (LSA) is a basic communication means of the OSPF routing protocol for the Internet Protocol (IP). It communicates the router’s local routing topology to all other local routers in the same OSPF area.
What is the difference between an LSA 3 and an LSA 4?
So, essentially Type 3 is used to advertise routes external to an area (including default routes) whereas the Type 4 is used to propagate the information about the ASBR router.
What is LSA 7 and how it can be used?
LSA Type 7 (NSSA External LSA) packets are used for some special area types that do not allow external distributed routes to go through and thus block LSA Type 5 packets from flooding through them, LSA Type 7 packets act as a mask for LSA Type 5 packets to allow them to move through these special areas and reach the …
What are LSA types?
OSPF LSA Types Explained
- LSA Type 1: Router LSA.
- LSA Type 2: Network LSA.
- LSA Type 3: Summary LSA.
- LSA Type 4: Summary ASBR LSA.
- LSA Type 5: Autonomous system external LSA.
- LSA Type 6: Multicast OSPF LSA.
- LSA Type 7: Not-so-stubby area LSA.
- LSA Type 8: External attribute LSA for BGP.
Why is type 4 LSA required?
LSA 4 is generated by the ABR. Link ID in that is the router ID of ASBR and Adv. Router is the ASBR itself. LSA 4 is required to tell the routers in other areas how to reach the ASBR to get to external network eventually.
What is Type 3 LSA?
The Summary (Type 3) LSA is used for advertising prefixes learned from the Type 1 and Type 2 LSAs into a different area. The Area Border Router (ABR) is the OSPF device that separates areas and it is this device that advertises the Type 3 LSA.
Why is LSA type 4 needed?
Who generates Type 4 LSA?
The type 4 LSA was generated by ABR R1 and describing the ASBR with the router ID 3.3.
What is LSA in routing?
Link State Advertisements (LSAs) are messages communicated via multicast to other routers in the OSPF domain. They are sent from internal routers to the DR/BDR routers to announce changes. This communication occurs on multicast address 224.0. 0.6.
What is a Type 5 LSA?
OSPF creates a type 5 LSA for a subnet that is injected into OSPF from an external source. To inject the route, the autonomous System Border Router (ASBR), which is by definition a router that connects to a non-OSPF routing domain, uses the redistribute command.
What is a Type 3 LSA?
Why is LSA 4 required?