10 Questions
What is the primary function of Type 1 LSAs in OSPF?
To identify the router and its attached links
Which type of LSA is sent by designated routers (DRs) on multi-access links?
Type 2 LSAs
What is the primary purpose of Type 3 LSAs in OSPF?
To summarize the information from other LSAs
Which type of LSA is used to convey information about IP subnets in other areas?
Type 3 LSAs
What is the primary purpose of Type 4 LSAs in OSPF?
To provide instructions on how to reach an ASBR
Which type of LSA is sent by Autonomous System Boundary Routers (ASBRs)?
Type 5 LSAs
What is the primary difference between Type 4 and Type 5 LSAs?
Type 4 LSAs are sent by ABRs, while Type 5 LSAs are sent by ASBRs
Which type of LSA is used to convey information about a single IP subnet that has been redistributed into OSPF?
Type 5 LSAs
Which type of LSA is confined to the area in which it was originated?
Type 1 LSAs
What is the primary purpose of Type 2 LSAs in OSPF?
To describe the link between multiple routers
Study Notes
OSPF LSAs Overview
- There are five main types of LSAs in OSPF: Type 1, Type 2, Type 3, Type 4, and Type 5.
- Each type of LSA has a specific purpose and is used to convey different information.
Type 1 LSAs (Router LSAs)
- Sent by every OSPF router.
- Identify the router and links it is attached to.
- Include information about the link, such as IP network, subnet mask, and cost.
- Used by other routers in the area to rebuild a topology map of the local area.
- Confined to the area in which it was originated.
Type 2 LSAs (Network LSAs)
- Sent by designated routers (DRs) on multi-access links.
- Include information about the multi-access link.
- Confined to the local area.
- Used to describe the link between multiple routers.
Type 3 LSAs (Summary LSAs)
- Sent by Area Border Routers (ABRs).
- Contain IP networks from foreign areas.
- Summarize the information from Type 1 and Type 2 LSAs.
- Used to convey information about IP subnets in other areas.
- Allow for IP summarization.
Type 4 and Type 5 LSAs
- Used for external routes.
- Type 5 LSAs are used for external networks redistributed into OSPF.
- Type 4 LSAs are used to provide instructions on how to reach an ASBR in a foreign area.
Type 5 LSAs (External LSAs)
- Sent by Autonomous System Boundary Routers (ASBRs).
- Contain a single IP subnet that has been redistributed into OSPF.
- Forwarded unchanged throughout the OSPF domain.
Type 4 LSAs (ASBR Summary LSAs)
- Sent by ABRs whenever an ASBR exists in a foreign area.
- Provide instructions on how to reach the ASBR.
- Used to help routers in other areas reach the redistributed network.
OSPF LSAs Overview
- There are five main types of LSAs in OSPF: Type 1, Type 2, Type 3, Type 4, and Type 5, each with a specific purpose and conveying different information.
Type 1 LSAs (Router LSAs)
- Sent by every OSPF router to identify itself and its attached links.
- Contain information about the link, including IP network, subnet mask, and cost.
- Used by other routers in the area to rebuild a topology map of the local area.
- Confined to the area in which it was originated.
Type 2 LSAs (Network LSAs)
- Sent by designated routers (DRs) on multi-access links.
- Contain information about the multi-access link.
- Confined to the local area.
- Used to describe the link between multiple routers.
Type 3 LSAs (Summary LSAs)
- Sent by Area Border Routers (ABRs).
- Contain summarized information from Type 1 and Type 2 LSAs.
- Used to convey information about IP subnets in other areas.
- Allow for IP summarization.
Type 4 and Type 5 LSAs
- Used for external routes.
- Type 5 LSAs are used for external networks redistributed into OSPF.
- Type 4 LSAs provide instructions on how to reach an ASBR in a foreign area.
Type 5 LSAs (External LSAs)
- Sent by Autonomous System Boundary Routers (ASBRs).
- Contain a single IP subnet that has been redistributed into OSPF.
- Forwarded unchanged throughout the OSPF domain.
Type 4 LSAs (ASBR Summary LSAs)
- Sent by ABRs whenever an ASBR exists in a foreign area.
- Provide instructions on how to reach the ASBR.
- Used to help routers in other areas reach the redistributed network.
Learn about the five main types of LSAs in OSPF including their purpose and the information they convey. Understand the role of Type 1 LSAs in identifying routers and rebuilding topology maps.
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