Show ip ospf route cisco

Introduction

OSPF, being a link-state protocol, allows for every router in the network to know of every link and OSPF speaker in the entire network. From this picture each router independently runs the Shortest Path First (SPF) algorithm to determine the best path through the network.

All of this information is stored in the "Link State Database" (LSDB). Every network engineer has seen the LSDB at some point by running show ip ospf database but few actually know how to read the details.

Show ip ospf neighbor

By looking only at the LSDB we should have enough information to draw a topology diagram from scratch.

Link State Advertisements

OSPF uses "Link State Advertisements" (LSAs) to provide information about links and link-costs to neighboring OSPF speakers.

OSPF defines multiple LSAs, which all serve a different purpose.

LSA Type	Who Generates the LSA?	What is Accomplished?
Type 1 - Router LSA	Every router in every area	How routers advertise their connected interfaces
Type 2 - Network LSA	DRs on all non-point-to-point links	The DR collects all the Type 1 LSAs and s show ip ospf route ospf network example