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

OSPF Timers: Hello and Dead Intervals Explained

OSPF Hello and Dead timers must match on both sides or neighbors never form. Here is how to check them, change them safely, and tune for faster convergence.

Mar 24, 2026 1 min read

OSPF

OSPF Virtual Links Configuration

Virtual links patch a discontiguous Area 0 by tunneling through a transit area. Configuration is simple, but treat them as a temporary fix, not a permanent design.

Mar 24, 2026 1 min read

OSPF

OSPF Stub Area Configuration (Stub, Totally Stubby, NSSA)

Stub, Totally Stubby, and NSSA areas each block different LSA types to shrink the LSDB. Here is the config, the verification output, and when to pick each one.

Mar 24, 2026 2 min read

OSPF

OSPF Authentication Configuration (Plain Text and MD5)

OSPF supports plain-text, MD5, and SHA authentication at the interface or area level. Here is how to configure each, why MD5 is the production default, and how to verify.

Mar 24, 2026 3 min read

OSPF

Configuring Multi-Area OSPF on Cisco Routers

Multi-area OSPF across Area 0, 10, and 20 with two ABRs. Full R1 to R5 config plus show commands to confirm inter-area routes and ABR behavior.

Mar 24, 2026 6 min read

OSPF

How to Advertise a Default Route in OSPF

The default-information originate command injects 0.0.0.0/0 as a Type 5 LSA and turns the router into an ASBR. Here is the syntax, the always option, and verification.

Mar 24, 2026 4 min read