Subnetting (EIGRP), Computer Networking

#questiGE 1-A


• Consolidate EIGRP knowledge.
• Introduce the Route Redistribution concept.
• Introduce the EIGRP External Routes concept.
• Introduce the Default Metric concept.


OTB Inc. is having trouble on their network and needs help. Part of their network has no connectivity.



According to the report, network 1 and network 2 are not able to reach network 3. As shown on OTB Network Topology above, OTB Inc. has 2 routing protocols running due transition issues. The goal is to have only one protocol running within the network but for now the older protocol must be kept. In order to achieve full connectivity, OTB routes generated by one routing protocol must be injected into the other one.

Step 1 – Checking the routers

You connect to R3 via console port to check its configuration. R3 is a RIPv2 speaker and a quick look at its configuration does not show anything unexpected: RIPv2 is correctly configured at R3, all R3 interfaces are up but R3 learned no routes via RIPv2.
Still from R3, you issue a few pings: pings to a few PCs under network 3 and to R4’s serial 0/0 interface are successful. Pings to R2’s interfaces and to R1’s interfaces fail.
You also issue a few pings from a few PCs under network 3 towards a few PCs under network 1 but all of such pings fail.

A quick look into R3’s routing table reveals it has no default route or routes to the EIGRP side of OTB’s network. Since R3’s configuration is correct, you assume some router was incorrectly configured and thus, wrongly advertising routes.
Since R3 is not learning routes from the EIGRP side, you decided to check EIGRP configuration into the EIGRP routers. You move to the EIGRP side, switch the console cable to R1 and check its configuration.

Once more, the configuration is correct: all R1’s interfaces are up, EIGRP is correctly configured and R1 has EIGRP routes installed into its routing table. R1 has a default route pointing to R4’s fa0/0 which was learnt via EIGRP from R4.
R1 also has EIGRP routes to network 3 ( Such routes were learnt from R4 and are flagged as external EIGRP routes.

Question 1:
What is the meaning of an EIGRP External Route?
Question 2:
How are EIGRP external routes identified?
Question 3:
What is Two-Way Redistribution?
Question 4:
Why was the default metric set to 3?
For more info about route redistribution visit:
How do the EIGRP generated routes appear into R3’s routing table? Are they flagged as EIGRP routes or as RIP routes?
Question 6 – Challenge Question (OPTIONAL):
Is network 3 able to reach the Internet or any other network out of OTB? Explain. If not, what should be changed to allow network 3 reaching networks other than OTB’s?
Posted Date: 2/27/2013 8:34:25 AM | Location : United States

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