OSPF

Open Shortest Path First, the link-state IGP behind most enterprise networks. Articles tagged OSPF cover neighbor relationships, LSA types, areas, DR/BDR election, and Cisco IOS XE configuration.

46 posts

OSPF

Interface-Based OSPF Configuration (ip ospf Command)

Interface-based OSPF configuration (ip ospf [process] area) skips wildcard masks and makes per-port membership obvious. Here is when to use it and how.

Mar 24, 2026 4 min read

OSPF

OSPF Passive Interface Configuration

Passive interface stops OSPF Hellos on user VLANs while still advertising the subnet. Learn how it works, how to configure it, and how to verify without breaking adjacencies.

Mar 24, 2026 7 min read

OSPF

How to Configure Single-Area OSPF on Cisco Routers (Step-by-Step)

A full R1/R2/R3 single-area OSPF lab with IP plan, router ospf config, and the show commands that prove neighbors are Full and routes are installed.

Mar 24, 2026 9 min read

OSPF

OSPF Router ID: What It Is and How to Configure It

OSPF picks a Router ID from manual config, then the highest loopback, then the highest physical IP. Here is the selection order, examples, and how to lock it down.

Mar 24, 2026 6 min read

OSPF

How OSPF Calculates Metric and Cost

OSPF cost is Reference Bandwidth / Interface Bandwidth, and the default 100 Mbps reference turns every gigabit link into cost 1. Here is how to fix it properly.

Mar 24, 2026 6 min read

OSPF

OSPF Network Types Explained (Broadcast, Point-to-Point, NBMA)

OSPF has four network types: broadcast, point-to-point, NBMA, and point-to-multipoint. Each changes DR election and Hello behavior. Here is when to use which.

Mar 24, 2026 1 min read