OSPF (Open Shortest Path First) Flashcards
What does OSPF stand for?
Open Shortest Path First.
What type of routing protocol is OSPF?
Link-state routing protocol.
What is an OSPF Router ID?
A 32-bit number that uniquely identifies a router in an OSPF network.
What are the OSPF area types?
Backbone area (Area 0), Stub area, Totally Stubby area, Not-So-Stubby area (NSSA).
What is the purpose of an OSPF Hello packet?
To discover and maintain neighbor relationships.
How often are OSPF Hello packets sent by default?
Every 10 seconds on broadcast and point-to-point links.
What are the OSPF states?
Down, Init, Two-Way, ExStart, Exchange, Loading, Full.
At which state do OSPF routers start exchanging link-state information?
Exchange state.
What are the different OSPF network types?
Broadcast, Non-Broadcast Multi-Access (NBMA), Point-to-Point, Point-to-Multipoint.
Which OSPF network type elects a Designated Router (DR) and Backup Designated Router (BDR)?
Broadcast and NBMA.
What metric does OSPF use to calculate the best path?
Cost, which is based on the bandwidth of the links.
What is the default OSPF dead interval?
40 seconds on broadcast and point-to-point links.
What is the backbone area in OSPF?
Area 0, which is the central area to which all other areas must connect.
What are the different types of OSPF LSAs (Link-State Advertisements)?
Type 1 (Router LSA), Type 2 (Network LSA), Type 3 (Summary LSA), Type 4 (ASBR Summary LSA), Type 5 (External LSA), Type 7 (NSSA LSA).
What is the role of the Designated Router (DR) in OSPF?
To reduce the number of adjacencies and LSA exchanges on multi-access networks.
How is the Designated Router (DR) elected in OSPF?
Based on the highest OSPF priority, with ties broken by the highest Router ID.
What types of authentication does OSPF support?
Null, Plaintext, and MD5 authentication.
What is OSPF Virtual Link?
A logical connection used to connect an OSPF area to the backbone area if direct connectivity is not possible.
What is OSPF Route Summarization?
The process of consolidating multiple OSPF routes into a single summary route to reduce the size of the routing table.
What is a Type 1 LSA?
Router LSA. Generated by each router to describe its own links and states. Confined to the originating area.
What is a Type 2 LSA?
Network LSA. Generated by the Designated Router to describe the routers attached to a multi-access network. Confined to the originating area.
What is a Type 4 LSA?
ASBR Summary LSA. Generated by ABRs to advertise the presence of an Autonomous System Boundary Router (ASBR) to other areas.
What is a Type 3 LSA?
Summary LSA. Generated by Area Border Routers (ABRs) to advertise networks from one area to another.
What is a Type 5 LSA?
External LSA. Generated by ASBRs to advertise external routes (routes to destinations outside the OSPF autonomous system) throughout the entire OSPF domain.
What is a Type 7 LSA?
NSSA LSA. Generated in Not-So-Stubby Areas (NSSAs) by ASBRs to describe external routes. Translated to Type 5 LSAs by ABRs when exiting the NSSA.
Which LSAs are confined to the originating area?
Type 1 (Router LSA) and Type 2 (Network LSA).
Which LSAs are used to share information between OSPF areas?
Type 3 (Summary LSA) and Type 4 (ASBR Summary LSA).
Which LSA is generated by ASBRs to advertise external routes?
Type 5 (External LSA).
What is the function of Type 7 LSAs in OSPF?
Generated in NSSAs by ASBRs to describe external routes and translated to Type 5 LSAs by ABRs when exiting the NSSA.
