OSPF operates differently on different link types. On Ethernet (broadcast), it elects a DR/BDR. On a point-to-point link (PPP, P2P serial, GRE), no election - both ends form an adjacency directly. There are also non-broadcast (NBMA) types for legacy Frame Relay, and point-to-multipoint variants. This lab compares the two most common types - broadcast and point-to-point - using the OSPF Reference Lab.
What you will learn
- The five OSPF network types and what each is for
- Why DR/BDR election happens on broadcast and NOT on P2P
- How to read
show ip ospf interfacefor network type details - How to manually set the OSPF network type with
ip ospf network - Why P2P is the right network type for GRE tunnels (even though they sit on Ethernet)
What this lab does NOT cover
- NBMA (Non-Broadcast Multi-Access) - Frame Relay-era, rarely used in 2026
- Loopback network type (irrelevant for adjacency)
Topology
Download the OSPF Reference Lab .yaml
The PingLabz OSPF Reference Lab - 4 iol-xe routers across Area 0 (broadcast LAN) and Area 30 (P2P). R1 is ASBR, R2 is ABR + DR, R3 is BDR, R4 is internal Area 30.
The five network types
Ethernet, default
TypeBroadcast
DR/BDR?Yes
Hello timer10 seconds
Serial links, PPP, GRE
TypePoint-to-Point
DR/BDR?No
Hello timer10 seconds
Frame Relay multipoint, legacy
TypeNBMA (Non-Broadcast)
DR/BDR?
Yes (manual configuration)
Hello timer30 seconds
Hub-and-spoke topologies, NBMA without manual neighbor config
TypePoint-to-Multipoint
DR/BDR?No
Hello timer30 seconds
Rare. Specific Frame Relay use case.
Type
Point-to-Multipoint Non-Broadcast
DR/BDR?No
Hello timer30 seconds
