OSPF Summarization Discard Route

Posted by September 20, 2011 in OSPF

Scenario:

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…

Goal:

  • 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 3.3.3.3 /24.
  • Configure router Shapeir to summarize network 3.3.3.0 /24 to 3.0.0.0 /8.
  • Configure router Shapeir so it doesn’t add a null0 entry in its routing table.

IOS:

c3640-jk9s-mz.124-16.bin

Topology:

OSPF Summarization Discard Route Network Topology

Video Solution:

Configuration Files

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19 Comments

  6. 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.

  8. There can be a minor correction.
    4th Goal says "Configure router Shapeir to summarize network 3.3.3.0 /24 to 3.0.0.0 /8."

    This means Shapeir router should have a 3.3.3.0/24 route but it is getting a /32 route. In order to get a 3.3.3.0/24 route on Shapeir router below should be configured on the Spielburg route:

    inter loopback0
    ip ospf network point-to-point
    end

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

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

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

  15. 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

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

    ! Router Shapeir
    !
    router ospf 1
    log-adjacency-changes
    area 1 range 3.0.0.0 255.0.0.0
    network 192.168.12.0 0.0.0.255 area 0
    network 192.168.23.0 0.0.0.255 area 1
    distribute-list prefix 1 in
    !
    ip prefix-list 1 seq 5 deny 3.0.0.0/8
    ip prefix-list 1 seq 10 permit 0.0.0.0/0 le 32

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