OSPF Network Types : Broadcast/NB, NBMA,P2P

I would like to know, based on what criteria should I determine if my Network Type should be:
Broadcast, Non Broadcast, Point to Point, Multicast, NBMA,etc....

I have done some reading, but there is a lot of confusion.

Any clarification  on this topic will be very much appreciated

Thank you
jskfanAsked:
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AkinsdConnect With a Mentor Network AdministratorCommented:
This info should help
For more info, see the link  at the bottom

Non-Broadcast
    The Non-Broadcast network type is the default for OSPF enabled frame relay physical interfaces.
    Non-Broadcast networks requires the configuration of static neighbors; hello’s are sent via unicast.
    The Non-Broadcast network type has a 30 second hello and 120 second dead timer.
    An OSPF Non-Broadcast network type requires the use of a DR/BDR

 Broadcast
    The Broadcast network type is the default for an OSPF enabled ethernet interface.
    The Broadcast network type requires that a link support Layer 2 Broadcast capabilities.
    The Broadcast network type has a 10 second hello and 40 second dead timer.
    An OSPF Broadcast network type requires the use of a DR/BDR.

 Point-to-Point
    A Point-to-Point OSPF network type does not maintain a DR/BDR relationship.
    The Point-to-Point network type has a 10 second hello and 40 second dead timer.
    Point-to-Point network types are intended to be used between 2 directly connected routers.

 Point-to-Multipoint
    OSPF treats Point-to-Multipoint networks as a collective of point-to-point links.
    Point-to-Multipoint networks do not maintain a DR/BDR relationship.
    Point-to-Multipoint networks advertise a hot route for all the frame-relay endpoints.
    The Point-to-Multipoint network type has a 30 second hello and 120 second dead timer.

 Point-to-Multipoint Non-Broadcast
    Same as Point-to-Multipoint but requires static neighbors. Used on Non-broadcast layer 2 topologies.
    Gives you the ability to define link cost on a per neighbor basis.

 Loopback
    The default OSPF network type; only available to loopback interfaces.
    Advertises the interface as a host route; changeable by configuring the interface as point-to-point.

https://www.freeccnaworkbook.com/workbooks/ccna/configuring-ospf-network-types
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jskfanAuthor Commented:
So far I have done some reading and found out
Point to Point is when you have a Serial Link connecting 2 Routers and the encapsulation is HDLC or PPP
NBMA is used in Frame Relay and ATM networks
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jskfanAuthor Commented:
I believe Point to Point can be on Serial Link and it does not have to be encapsulated.
Broadcast is on Ethernet Network and it can be Point to Point and it can be Point to MultiPoint (Hub and Spokes)

There is also Point-to-Multipoint non-broadcast Network, I am not sure if this is on Serial Links or Ethernet Links?
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JustInCaseConnect With a Mentor Commented:
Point to Point is when you have a Serial Link connecting 2 Routers and the encapsulation is HDLC or PPP

Broadcast is on Ethernet Network
Those links are by default marked as point-to-point or broadcast links, but you can change connection type manually if you need to under interface:

interface fa0/0
R1(config-if)#ip ospf network ?
  broadcast            Specify OSPF broadcast multi-access network
  non-broadcast        Specify OSPF NBMA network
  point-to-multipoint  Specify OSPF point-to-multipoint network
  point-to-point       Specify OSPF point-to-point network

Open in new window

Prior to configure both sides of interface as  point-to-point (type Broadcast):
FastEthernet0/0 is up, line protocol is up
  Internet Address 192.168.0.2/24, Area 0
  Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 10
  Transmit Delay is 1 sec, State BDR, Priority 1
  Designated Router (ID) 2.2.2.2, Interface address 192.168.0.1
  Backup Designated router (ID) 1.1.1.1, Interface address 192.168.0.2
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    oob-resync timeout 40
    Hello due in 00:00:04
  Supports Link-local Signaling (LLS)
  Cisco NSF helper support enabled
  IETF NSF helper support enabled
  Index 1/1, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 1, maximum is 1
  Last flood scan time is 0 msec, maximum is 0 msec
  Neighbor Count is 1, Adjacent neighbor count is 1
    Adjacent with neighbor 2.2.2.2  (Designated Router)
  Suppress hello for 0 neighbor(s)

Open in new window


interface fa0/0
ip ospf network point-to-point
After to configure both sides of interface as  point-to-point:

FastEthernet0/0 is up, line protocol is up
  Internet Address 192.168.0.1/24, Area 0
  Process ID 1, Router ID 2.2.2.2, Network Type POINT_TO_POINT, Cost: 10
  Transmit Delay is 1 sec, State POINT_TO_POINT
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    oob-resync timeout 40
    Hello due in 00:00:02
  Supports Link-local Signaling (LLS)
  Cisco NSF helper support enabled
  IETF NSF helper support enabled
  Index 1/1, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 1, maximum is 2
  Last flood scan time is 0 msec, maximum is 0 msec
  Neighbor Count is 1, Adjacent neighbor count is 1
    Adjacent with neighbor 1.1.1.1
  Suppress hello for 0 neighbor(s)

Open in new window


Point-to-Multipoint non-broadcast Network - is typically frame relay network with hub and spoke topology.
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Craig BeckCommented:
Do you have a real-world use-case, or are you just asking for certification purposes, for example?

If it helps, on networks nowadays using standard Ethernet technologies you'd use point-to-point where you have a pure L3 link between two routers.  You'd use point-to-multipoint where you have more than two routers on the same L2 segment using the same subnet.

If you're using WAN technologies between routers you might need to use NBMA but I'm sure the two I mention are the most prevalent these days.
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jskfanAuthor Commented:
You'd use point-to-multipoint where you have more than two routers on the same L2 segment using the same subnet.
If it is Ethernet I believe you will still use Broadcast and not point-to-multipoint
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Craig BeckConnect With a Mentor Commented:
If it is Ethernet I believe you will still use Broadcast and not point-to-multipoint

Not always. Sometimes you don't want to, or can't, use broadcast (multicast). I apologise for not making this clear. You would use broadcast on a pure L2 Ethernet segment but probably not over an IPSEC tunnel, for example.
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jskfanAuthor Commented:
Thank you Guys
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