OSPF per Neighbor Cost

Posted by September 20, 2011 in OSPF

Scenario:

The local fish trading market needs your help with their OSPF network. It seems their routers are unable to change the bandwidth or cost on the interfaces so you need to use another solution to influence OSPF routing…sounds fishy!

Goal:

  • All IP addresses have been preconfigured for you.
  • Configure OSPF on all routers. Achieve full connectivity.
  • Configure a loopback0 interface with IP address 1.1.1.1 /32 on router Salmon and Herring.
  • Advertise the loopback0 interface on router Salmon and Herring.
  • Configure your network so router Barracuda sends all traffic for 1.1.1.1 /32 to router Herring. You are not allowed to change the bandwidth or cost on the interface.

It took me 1000s of hours reading books and doing labs, making mistakes over and over again until I mastered all the protocols for CCNA.

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Does this sound interesting to you? Take a look here and let me show you how to Master CCNA!

IOS:

c3640-jk9s-mz.124-16.bin

Topology:

OSPF per neighbor cost 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.

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Written by René Molenaar - CCIE #41726

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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

2 Comments

  1. Hi,

    I’ve doubt regarding the solution.
    the command
    neighbor x.x.x.x cost 10 tells the router that neighbor have the cost 10 ?
    If I’ve configured
    neighbor x.x.x.x cost 0 , tells the router that neighbor can’t be DR/BDR, alright ?
    I’m not sure about the cost, if the cost that i’m setting is from my neighbor or mine.

    thx.

  2. Ciao Renato,
    perhaps I can answer you:

    yes, the command
    neighbor x.x.x.x cost 10
    tells the router that the link to reach the neighbor has a cost of 10.
    But do not mislead the priority (parameter evaluted for the DR/BDR election on the OSPF netw types where the election takes place) with the cost (metric used for route selection).
    Moreover the cost cannot be zero, minimum 1, max 16777215.
    Valid values for the priority are in the range 0-255 (255 is the highest priority)
    Setting the priority to 0 on the router interface, make it ineligible to DR or BDR on the OSPF network connected to that interface

    hth

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