OSPF Summarization Discard Route


Ever since you encountered a router your quest has been to become a succesful network engineer. Your career is prosperous and there isn’t a bit that you haven’t slain before. This time however you are running into trouble with one of your OSPF routers. It seems one of your routers is installing a null0 route whenever you do summarization and this is something you don’t want to happen…


  • All IP addresses have been preconfigured for you.
  • Configure OSPF and use the correct areas.
  • Configure a loopback0 interface on router Spielburg with network address /24.
  • Configure router Shapeir to summarize network /24 to /8.
  • Configure router Shapeir so it doesn’t add a null0 entry in its routing table.




OSPF Summarization Discard Route Network Topology

Video Solution:

Configuration Files

You need to register to download the GNS3 topology file. (Registration is free!)

Once you are logged in you will find the configuration files right here.

Opt In Image
Do you want your CCNA or CCNP Certificate?

The How to Master series helps you to understand complex topics like spanning-tree, VLANs, trunks, OSPF, EIGRP, BGP and more.

Written by René Molenaar - CCIE #41726

You May Also Like

About the Author: Rene Molenaar

René - CCIE #41726 is the creator of GNS3Vault.com where he shares CCNA, CCNP and CCIE R&S labs. He also blogs about networking on http://networklessons.com


  1. i redistributed a static route and summarized it at the ASBR.
    no null0 interface and proper network advertised into area 0
    so there was an easier way than redistribution… thanks for the tip Rene.

  2. There can be a minor correction.
    4th Goal says "Configure router Shapeir to summarize network /24 to /8."

    This means Shapeir router should have a route but it is getting a /32 route. In order to get a route on Shapeir router below should be configured on the Spielburg route:

    inter loopback0
    ip ospf network point-to-point

    1. Good eye man! Loopback are automatically declared as stub networks otherwise and forced into a /32.

  3. The following command is the main goal of this lab

    Shapeir(config)#router ospf 1
    Shapeir(config-router)#no discard-route internal

  4. Hi Admin,
    I am just a new to this GNS3 Vault forum , currently i am using Gns3 0.8.6 version in laptop,
    when check “config files” attached in the page , its contains “.gns3” file , please let me know how to use it
    and open in GNS3 software

    Your help is very valuable for me , thanks

  5. Сan be solved by using the “distribute-list”:

    ! Router Shapeir
    router ospf 1
    area 1 range
    network area 0
    network area 1
    distribute-list prefix 1 in
    ip prefix-list 1 seq 5 deny
    ip prefix-list 1 seq 10 permit le 32

Comments are closed.