OSPF Supported Network Types: P2P, NBMA, P2MP, and Broadcast

H12-811 By islever Editorial Last updated

OSPF Principles and Configuration

Short answer

ABCD All four options represent valid OSPF network types: Point-to-Point, Non-Broadcast Multi-Access, Point-to-Multipoint, and Broadcast.

Question

Which of the following network types does OSPF support? (Choose all that apply.)
  1. Point-to-Point. Correct Answer
  2. Non-Broadcast Multi-Access. Correct Answer
  3. Point-to-Multipoint. Correct Answer
  4. Broadcast. Correct Answer

Key Takeaways

The main trap is assuming only 'Broadcast' (Ethernet) is native to OSPF, ignoring that P2P, NBMA, and P2MP are also standard, configurable network types.

This page explains that OSPF supports all four listed network types: Point-to-Point, Non-Broadcast Multi-Access, Point-to-Multipoint, and Broadcast. Correct answer is ABCD.

Common mistake: Selecting only ACD, mistakenly believing NBMA is not a valid OSPF network type due to its non-broadcast nature requiring manual neighbor configuration.

Expert Analysis

OSPF Network Types and Topology Support

The question asks which network types Open Shortest Path First (OSPF) supports. OSPF is a link-state routing protocol that categorizes interfaces into specific network types to determine how adjacencies are formed, how LSAs are flooded, and whether a Designated Router (DR) or Backup Designated Router (BDR) is elected.

Analysis of Options

  • A. Point-to-Point (P2P): This type is used on links connecting exactly two routers, such as PPP or HDLC serial links. OSPF treats these as point-to-point networks; no DR/BDR election occurs, and neighbors form adjacencies immediately. This is a supported type.
  • B. Non-Broadcast Multi-Access (NBMA): This type applies to multi-access networks that do not support broadcast traffic, such as Frame Relay or ATM. OSPF supports this type, but it requires manual neighbor configuration (since broadcast/ multicast cannot be used for Hello packets) and typically involves DR/BDR elections. This is a supported type.
  • C. Point-to-Multipoint (P2MP): This type treats a NBMA network as a collection of individual point-to-point links between the local router and its neighbors. It does not elect a DR/BDR. OSPF supports this configuration to simplify NBMA topology management. This is a supported type.
  • D. Broadcast: This type is used on LAN segments like Ethernet where broadcast and multicast communication are possible. OSPF uses this type by default on Ethernet interfaces. It elects a DR and BDR to manage LSA flooding efficiently. This is a supported type.

Common Misconception

Some candidates may believe NBMA is not a "native" OSPF type because it requires special configuration (like ospf network-type nbma or static neighbors), whereas Broadcast is the default on Ethernet. However, all four are explicitly defined network types in the OSPF standard and vendor implementations (including Huawei H12-811). The comment suggesting "ACD is correct" because "B is wrong no multiaccess" is incorrect; NBMA stands for Non-Broadcast Multi-Access, meaning multiple routers share the media, but broadcast capability is lacking.

Exam Strategy Implication

Getting this wrong usually stems from confusing OSPF's default behavior with its supported capabilities. While Broadcast is the default on Ethernet, OSPF is designed to operate over various media types, including P2P, P2MP, and NBMA. Recognizing that OSPF is media-agnostic in its design helps avoid excluding valid network types.

Official Reference

https://support.huawei.com/enterprise/en/doc/EDOC1100096312/d4836a95/ospf-network-type

This link opens the official vendor documentation in a new tab.

Exam Strategy

When asked about 'supported' features in networking exams, always consider the full standard specification rather than just the most common default implementation. For OSPF, remember that while Broadcast is default on Ethernet, the protocol explicitly defines P2P, NBMA, and P2MP as distinct network types with specific adjacency and LSA behaviors. Do not exclude options based on 'complexity' or 'manual configuration requirements' unless the question specifies 'default' or 'automatic'.

Frequently Asked Questions

Does OSPF automatically elect a DR on Point-to-Point networks?

No. On Point-to-Point networks, OSPF forms adjacencies directly without electing a DR or BDR. DR/BDR elections only occur on Broadcast and NBMA network types.

What is the difference between NBMA and Point-to-Multipoint in OSPF?

NBMA requires manual neighbor configuration and elects a DR. Point-to-Multipoint treats the network as a set of point-to-point links, does not elect a DR, and can auto-discover neighbors if multicast is available.

More H12-811 FAQ →

Community Votes

A
34%
B
33%
C
33%

34% of anonymous learners picked answer A. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 6 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 6

  1. akamg 👍 3
    All of them https://support.huawei.com/enterprise/en/doc/EDOC1100096312/d4836a95/ospf-network-type
  2. IBB90704 👍 2
    Respuesta ABCD Pagina 250 R1-GigabitEthernet1/0/0] ospf network-type ? broadcast Specify OSPF broadcast network nbma Specify OSPF NBMA network p2mp Specify OSPF point-to-multipoint network p2p Specify OSPF point-to-point network
  3. lkhjk 👍 2
    ACD is correct. B is wrong no multiaccess.
  4. Chleong 👍 2
    Answer is All of them
  5. Fmoura17 👍 1
    Answer: A, B, C, and D All four are OSPF supported network types: A. Point-to-Point ✅ — Direct link between two routers (e.g., serial links). No DR/BDR election needed. B. Non-Broadcast Multi-Access (NBMA) ✅ — Multiple routers, no broadcast (e.g., Frame Relay). DR/BDR elected manually. C. Point-to-Multipoint ✅ — Treats multi-access network as a collection of point-to-point links. No DR/BDR election. D. Broadcast ✅ — Multiple routers with broadcast capability (e.g., Ethernet). DR/BDR election required.
Show 1 more comment
  1. TIConstecoin 👍 1
    ABCD, referencia a la documentación oficial

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