OSPF Network Types.

While looking at this topic in my route book it did not make a whole lot of sense to me, when I looked over and over over and began to summarize it to the point where I would be able to remember it I felt like a real idiot!  Since its not Broadcast it uses unicasts / Psuedo broadcasts.  I do not have the most common network ethernet / broadcast listed since I am going to have my next blog post dedicated to OSPF fundamental notes that are based off of OSPF broadcast / Ethernet.

 

1.)OSPF Over NBMA

 

 

-Ip Ospf network non-broadcast command

-Needs  DR

-Unicast Address from Dr to its Drothers

-Needs one Subnet

-Hello timers – 30 seconds Dead – 120 seconds

 

By removing the Broadcast capabilities it enables each router to make to send a Unicast opposed to a Multicast or a broad cast.  So r1 unicasts to R2 and same goes with R3.  This topology is setup as a hub and spoke.

 

This topology also requires a DR router.  Clearly, the Dr in this case is R1.  Make sure to set the OSPF priority of R2 and R3 to 0 so during the election process R1 is the DR.

 

 

 

 

 

 

 

2.)Point to Multi Point Network

 

-No Dr/BDR required

-Ip ospf network point-multipoint

-Ip Ospf network Point-Multipoint  – > command Must be used on connected interface

-Each Network in the above topology would Share a FULL relationship to each other.

-Interfaces Connecting to the cloud need to be one shared Subnet. /24 in this case.

 

 

3.)Point to Multi Point NBMA

 

-no DR/BDR

-Ip ospf network point-multipoint non-broadcast

-biggest difference here is removing the broadcast creating the Pseudo broadcast

-each neighbor is FULL

-hello timers – 30 seconds dead – 120

 

Biggest difference between Point to Multipoint network and point to Multipoint is the Unicast / PSEUDO broadcast.

 

 

 

 

4.)OSPF point to point Network type

 

 

-uses ip OSPF network point-to-point

-since it is p2p all routers have to be in the same area.

-R1 Will form a Full Adjacency NO DR

-NO DR

-Packets will use the Multicast OSPF address 224.0.0.5

-hello packets – 10 seconds 40 – dead packets

 

 

Summary

 

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Comments

  • ivan  On November 25, 2010 at 1:02 am

    cannot really read ur summary..

  • Sambit  On December 14, 2010 at 9:03 am

    Nice Explaination in simple language……..

    keen on ….. for other topics…

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