Module 1 - Single-Area OSPFv2 Concepts

Vocabulary flashcards focusing on definitions, packet types, operational states, and components of Single-Area OSPFv2 based on the lecture material.

OSPF

A link-state routing protocol developed as an alternative for the distance vector Routing Information Protocol (RIP) that offers faster convergence and scales to larger network implementations.

Link

An interface on a router, a network segment that connects two routers, or a stub network such as an Ethernet LAN connected to a single router.

Link-state

Information about the state of a link, which includes the network prefix, prefix length, and cost.

Adjacency Database

The neighbor table that lists all neighbor routers to which a router has established bi-directional communication, unique for each router, and viewed using the show ip ospf neighbor command.

Link-state Database (LSDB)

The topology table that lists information about all other routers in the network, where all routers within an area have an identical LSDB, viewed using the show ip ospf database command.

Forwarding Database

The routing table containing a list of best routes generated when the SPF algorithm is run on the link-state database, viewed using the show ip route command.

Shortest-Path First (SPF) Algorithm

The Dijkstra-based algorithm used by OSPF to create an SPF tree by placing each router at the root and calculating the shortest path based on cumulative cost.

Single-Area OSPF

An OSPF implementation where all routers reside in a single area, with area 0 being the recommended best practice.

Multiarea OSPF

An OSPF implementation using multiple areas in a hierarchical fashion where all areas must connect to the backbone area (area 0).

Area Border Router (ABR)

A router that interconnects different areas in a multiarea OSPF network.

OSPFv3

The OSPFv2 equivalent for exchanging IPv6 prefixes, which uses IPv6 as the network layer transport and runs processes independently from IPv4.

Hello Packet

The Type 1 OSPF packet used to discover neighbors, establish neighbor adjacencies, advertise agreed parameters, and elect the DR and BDR on multiaccess networks.

Database Description (DBD) Packet

The Type 2 OSPF packet used to check for database synchronization between routers.

Link-State Request (LSR) Packet

The Type 3 OSPF packet used by a router to request specific link-state records from another router.

Link-State Update (LSU) Packet

The Type 4 OSPF packet used to send specifically requested link-state records and forward routing updates containing LSA messages.

Link-State Acknowledgment (LSAck) Packet

The Type 5 OSPF packet used to acknowledge other received OSPF packet types.

Down State

The initial OSPF operational state where no Hello packets have been received on the interface, and the router begins sending Hello packets.

Init State

The OSPF operational state where Hello packets containing the Router ID of the sending router are received from a neighbor.

Two-Way State

The OSPF operational state where communication between two routers is bidirectional, and DR/BDR election occurs on multiaccess links.

ExStart State

The OSPF operational state where point-to-point routers decide which router initiates the DBD packet exchange and establish the initial DBD packet sequence number.

Exchange State

The OSPF operational state where routers exchange Database Description (DBD) packets to compare database information.

Loading State

The OSPF operational state where LSRs and LSUs are used to acquire additional route information, and routes are processed using the SPF algorithm.

Full State

The OSPF operational state where the link-state database of the router is fully synchronized with its neighbor.

OSPF Router ID

A 32-bit number formatted like an IPv4 address that uniquely identifies a specific router within an OSPF area.

224.0.0.5

The reserved All OSPF Routers IPv4 multicast address used to send Hello packets for neighbor discovery.

Designated Router (DR)

The router elected on a multiaccess network to serve as the collection and distribution point for LSAs sent and received.

Backup Designated Router (BDR)

The router elected on a multiaccess network to step in and assume the collection/distribution roles if the Designated Router (DR) fails.

DROTHER

A router on a multiaccess network that has not been elected as either the Designated Router (DR) or Backup Designated Router (BDR).