OSPF Tables Types and Examples: Quiz and Flashcards

Study Notes

OSPF uses three tables to accomplish its goals:
- Neighbor Table
- Topology Table (also referred to as the Link State Database or LSDB)
- Routing Table
The Neighbor Table:
- Maintained by every OSPF router
- Lists all directly connected OSPF routers
- Holds information such as the state of adjacency with each neighbor

Stores everything OSPF knows about the network topology
A single table that includes all link state advertisements (LSAs)
Each router has an identical LSDB, ensuring all routers have the same view of the network
This table is used to calculate the shortest path first (SPF) algorithm
It contains information about the network, including routers, links, and their respective states
The LSDB is a crucial component of OSPF, as it enables routers to make informed decisions about routing traffic
The table is updated dynamically as the network changes, ensuring OSPF routers always have an accurate view of the network topology
Stores everything OSPF knows about the network topology
A single table that includes all link state advertisements (LSAs)
Each router has an identical LSDB, ensuring all routers have the same view of the network
The Routing Table:
- The router's actual routing table
- Calculates best routes from the topology table and sends them to the routing table
- Decides which routes are best and makes them available in the routing table

5 packets are involved in every OSPF conversation:
- Hello Packets
- Database Descriptor (DBD) Packets
- Link State Request Packets
- Link State Update (LSU) Packets
- Link State Acknowledgement (LS ACK) Packets
Hello Packets:
- Sent periodically to the multicast address 224.0.0.5
- Allow routers to discover each other and determine whether to form an adjacency
DBD Packets:
- Send a summary of LSAs in the LSDB
- Spare routers from sending and receiving the full LSDB
- Routers can request specific LSAs they need
Link State Request Packets:
- Used to request specific LSAs from another router
LSU Packets:
- Send the requested LSAs to the requesting router
LS ACK Packets:
- Confirm receipt of LSU packets

OSPF uses three tables to operate: Neighbor Table, Topology Table (Link State Database or LSDB), and Routing Table
The Neighbor Table is maintained by every OSPF router, listing all directly connected OSPF routers and their adjacency states
The Topology Table (LSDB) stores the entire network topology, with each router having an identical LSDB for a shared network view
The Routing Table calculates best routes from the Topology Table and makes them available for routing decisions

5 packet types are used in OSPF conversations: Hello, Database Descriptor (DBD), Link State Request, Link State Update (LSU), and Link State Acknowledgement (LS ACK) packets
Hello Packets are periodically sent to the 224.0.0.5 multicast address to discover routers and form adjacencies
Database Descriptor (DBD) Packets summarize LSAs in the LSDB, allowing routers to request specific LSAs and avoiding full LSDB transfers
Link State Request Packets are used to request specific LSAs from other routers
Link State Update (LSU) Packets send requested LSAs to the requesting router
Link State Acknowledgement (LS ACK) Packets confirm receipt of LSU packets