Cisco 3, Module 1

to discover neighbors and build adjacencies between them

to ensure database synchronization between routers

to request specific link-state records from neighbor routers

to send specifically requested link-state records

DBD

LSR

hello

LSU

LSAck

It is a link-state database that represents the network topology.

After convergence, the table only contains the lowest cost route entries for all known networks.

The topology table contains feasible successor routes.

The table can be viewed via the show ip ospf database command.

When converged, all routers in an area have identical topology tables.

routers whose SPF trees are identical

routers that share the same router ID

routers that have the same link-state information in their LSDBs

routers that share the same process ID

SPF will run and determine which neighbor router is "down".

OSPF will run a new DR/BDR election.

A new dead interval timer of 4 times the hello interval will start.

OSPF will remove that neighbor from the router link-state database.

LSU, LSAck, Hello, DBD, LSR

Hello, LSAck, LSU, LSR, DBD

LSAck, Hello, DBD, LSU, LSR

Hello, DBD, LSR, LSU, LSAck

The SPF algorithm chooses the best path based on 30-second updates​.

It scales well in both small and large networks.

OSPF authentication is configured in the same way on IPv4 and IPv6 networks.​

Routers can be grouped into autonomous systems to support a hierarchical system.

forwarding database

adjacency database

link-state database

routing table

link-state database

routing table

neighbor table

static routes

dissemination of LSAs

redistribution of external routes into OSPF

summarizing routes between areas

maintaining the link-state database