EIGRP Enabler #1 – Answers

certskills
By certskills February 9, 2017 12:10

The first EIGRP Enabler exercise asked you to configure four routers, specifically to add the EIGRP network commands. This post lists the answers – simple enough.

 

The Topology

It is probably best to have the exercise post on the screen at the same time you look at this post. If not, for convenience, here’s a copy of the topology figure for this exercise.

EIGRP Enabler Topology

 

The Answers

I promised short, sweet, and to the point. Here are the answers!

 

Answers: Router R1

 

Answers: Router R2

 

Answers: Router R3

 

Answers: Router R4

 

Comments and Explanations – R1

For R1, you needed to start by identifying the various classful networks (class A, B, or C networks) used on the interfaces. Then, to configure one network command to match each classful network, just configure the network command with that classful network number, and with no wildcard mask. Simple enough.

In this case, R1 has five interfaces with IPv4 addresses, all of which are part of class B network 172.17.0.0. Therefore, R1 needs only a single command: network 172.17.0.0.

 

Comments and Explanations – R2

R2 requires the most thought. To get these commands totally correct per the requirements, you must:

  1. Begin with each interface’s IP address and subnet mask
  2. Calculate the subnet ID, which will be the first parameter in the network command
  3. Invert the subnet mask, which will be the second parameter in the network command

Because of how the exercise is worded, you should have two network commands, one matching the subnet off each of the interfaces on R2.

 

Comments and Explanations – R3

R3 requires the least thought of the three requirements. To match a single IP address, use wildcard mask of 0.0.0.0. For the number preceding the wildcard mask in the network command, use the interface IP address. The result: each network command matches an interface IP address, and only that address, enabling EIGRP on that interface.

In this case, with two interfaces with IPv4 addresses, R3 needs two network commands, as shown in Example 3.

 

Comments and Explanations – R4

The requirements ask us to use the same logic to match each subnet as we used with router R2. The only twist here is that the subnet ID on one interface isn’t quite as obvious, and if you got in a hurry, you might have configured an incorrect subnet ID. Interface address 172.17.20.4, with mask 255.255.240.0, is in subnet 172.17.16.0, resulting in a correct command of network 172.17.16.0 0.0.15.255.

 

EIGRP Enabler #1
OSPFv2 Enabler #2
certskills
By certskills February 9, 2017 12:10
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4 Comments

  1. Smite February 14, 19:58

    Thanks. Excellent. Looking for the next enabler.

    Reply to this comment
  2. aaron February 16, 07:31

    Your blog is great it helps me learn a lot, any idea when your new network simulator for the 200-125 exam will be released? I’ve been waiting to buy it, but the release date keeps getting delayed.

    Reply to this comment
    • certskills Author February 16, 07:59

      Hi Aaron,
      Thanks!
      On the Sim, couple of answers. First, I don’t know the release schedule (see next). But the normal process the publisher follows is to give you a free upgrade offer. If you buy the old Sim from the publisher, follow the rules, you get a free upgrade when the new is out. Those have been posted on the publisher’s web sites for a while, BUT… I just checked the web site, and the old sim web pages and notices of the free upgrade path seem to have been removed from the site (probably already replaced with pages for the new sim). So… if you like that idea, and you asked the publisher, maybe you could buy the old now and free upgrade in what looks like now 4-6 weeks (assuming the date doesn’t move again). That’s reasonable in that the old vs. new is about 70-80% overlap of CLI topics, so you can learn a lot with the old.

      On a more personal note, I don’t know the Sim dates because I’m not involved in the product any more. They give me cover credit because I was the primary networking person working on the Sim for the first edition (and I was involved a little for the 2nd edition). These new ones will be the 3rd edition or version, and I’m not involved at all. So I don’t know the schedule, likelihood of slipping the dates, etc. Sorry about that!
      Wendell

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