OSPF LSA Types Explained

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Complete Understanding of OSPF LSA Types Is The Cornerstone To OSPF Network Design

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OSPF LSA Types Explained

  1. 1. LSA Types Explained Complete Understanding of LSA Types Is The Cornerstone To Understanding OSPF Areas and OSPF Area Behaviors Complete Understanding of OSPF Area Behaviors Is The Cornerstone of Good OSPF Network Design and Traffic Flow
  2. 2. OSPF LSA Types Explained
  3. 3. LSA Type 1 (Router LSA)Generated by all routers in an area to describe their directly attached links (Intra-area routes). These do not leave the area.
  4. 4. LSA Type 2 (Network LSA)Generated by the DR of a broadcast or Nonbroadcast segment to describe the neighbors connected to the segment. These do not leave the area.
  5. 5. LSA Type 3 (Summary LSA)Generated by the ABR to describe a route to neighbors outside the area. (Inter-area routes)
  6. 6. LSA Type 4 (Summary LSA)Generated by the ABR to describe a route to an ASBR to neighbors outside the area.
  7. 7. LSA Type 5 (External LSA)Generated by ASBR to describe routes redistributed into the area. These routes appear as E1 or E2 in the routing table. E2 (default) uses a static cost throughout the OSPF domain as it only takes the cost into account that is reported at redistribution. E1 uses a cumulative cost of the cost reported into the OSPF domain at redistribution plus the local cost to the ASBR.
  8. 8. LSA Type 6 (Multicast LSA)Not supported on Cisco routers
  9. 9. LSA Type 7 (NSSA LSA)Generated by an ASBR inside a NSSA to describe routes redistributed into the NSSA. LSA 7 is translated into LSA 5 as it leaves the NSSA. These routes appear as N1 or N2 in the ip routing table inside the NSSA. Much like LSA 5, N2 is a static cost while N1 is a cumulative cost that includes the cost up to the ASBR.

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