What is router LSA and network LSA?

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 does network link LSA mean?

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.

How many different types of LSA are there?

LSA Type 1: Router LSA. LSA Type 2: Network LSA. LSA Type 3: Summary LSA. LSA Type 4: Summary ASBR LSA.

How many OSPF LSA types are there?

6 Types of OSPF LSA.

Why is LSA type 4 needed?

Type 4 LSA 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 LSA and its types?

LSA Type 7: OSPF Not So Stubby Area (NSSA) External LSA. LSA Type 8: OSPF External Attributes LSA (OSPFv2) / Link Local LSA (OSPFv3) LSA Type 9: OSPF Link Scope Opaque (OSPFv2) / Intra Area Prefix LSA (OSPFv3) LSA Type 10: OSPF Area Scope Opaque LSA. LSA Type 11:OSPF AS (Autonomous System) Scope Opaque LSA.

Why is type 4 LSA required?

What are the 5 types of OSPF packets?

Packet types for OSPF

  • Hello packet. This packet is sent by the OMPROUTED server to discover OSPF neighbor routers and to establish bidirectional communications with them.
  • Database description packet.
  • Link-state update packet.
  • Link-state request packet.
  • Link-state acknowledgment packet.

What are OSPF network types?

There are 5 OSPF network types:

  • Non-Broadcast.
  • Broadcast.
  • Point-to-Multipoint.
  • Point-to-Multipoint Non-Broadcast.
  • Point-to-Point.

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 …

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 a Type 3 LSA?

LSA Type 3 – OSPF Summary LSA
LSA Type 3 (Summary LSA) packets are generated by Area Border Routers (ABR) to summarize its directly connected area, and advertise inter-area router information to other areas the ABR is connected to, with the use of a summary prefix (e.g 192.168.

What is a Type 5 LSA?

An OSPF type 5 LSA is originated by an Autonomous System Boundary Router (ASBR) and flooded within the OSPF area. These routes are generated by means of redistribution into OSPF from other protocols or by the redistribution of connected or static routes.

What are the 7 stages of OSPF?

The states are Down, Attempt, Init, 2-Way, Exstart, Exchange, Loading, and Full.

What is 2-way state in OSPF?

2-Way State
This state describes the Bi-Directional communication state, Bi- Directional means that each router has received the other’s Hello packet and that each router can see its own Router ID included within the Hello packet’s neighbor field.

What is the default network type in OSPF?

Broadcast The broadcast network type
The broadcast network type is the default network type for an OSPF-enabled Ethernet interface. It requires a link that supports Layer 2 broadcast.

What is the difference between LSA 5 and LSA 7?

Answer: The difference between Type-5 LSA and Type-7 LSA is that Type-7 LSA can live only into NSSA area, so it will never leave the NSSA area. Instead Type-5 LSA can be propagated to the other areas (backbone and non-backbone). – Both of them are generated by the ASBR.

What is Type 7 LSA?

What Is a Type 7 LSA? This is a type 7 LSA that is generated by an NSSA ASBR. Type 5 LSAs are not allowed in NSSA areas, so the NSSA ASBR generates a type 7 LSA instead, which remains within the NSSA. This type 7 LSA gets translated back into a type 5 by the NSSA ABR.

What is 2way state in OSPF?

2-Way. This state designates that bi-directional communication has been established between two routers. Bi-directional means that each router has seen the other’s hello packet. This state is attained when the router receiving the hello packet sees its own Router ID within the received hello packet’s neighbor field.

What are the five OSPF network types?

What are two basic OSPF network types?

OSPF can operate in one of two modes across a non-broadcast network: non-broadcast multi-access (NBMA) or point-to-multipoint. Each of these topologies tackles the absence of broadcast capability from a different direction.

What is E1 and E2 in OSPF?

E1 routes indicate cumulative cost to reach the destination i.e. int indicates cost to reach ASBR + cost to destination from ASBR. E2 route reflects cost only from the ASBR to destination. This is the default used by ospf for redistribution.

What is N1 and N2 routes in OSPF?

E1 or E2 or N1 or N2 type routes are based upon cost of the route. E2 or N2 routes tell OSPF routers to set the metric as the metric at the point of redistribution.(At the ASBR) E1 or N1 routes tell OSPF routers to add the internal costs to reach the ASBR to the cost set at the point of redistrbution (At the ASBR)

How does OSPF choose best path?

If there are multiple routes to a network with the same route type, the OSPF metric calculated as cost based on the bandwidth is used for selecting the best route. The route with the lowest value for cost is chosen as the best route.

What are the six OSPF route types?

This is the prefered path list that OSPF uses:

  • Intra-Area (O)
  • Inter-Area (O IA)
  • External Type 1 (E1)
  • NSSA Type 1 (N1)
  • External Type 2 (E2)
  • NSSA Type 2 (N2)