Cisco CCNA-CCNP Certification Exam Tutorial: EIGRP And Split Horizon


EIGRP is a major topic for your CCNA and CCNP studies, and one basic skill you’ll need to pass your Cisco certification exams is to identify situations where you need to enable or disable split horizon. EIGRP commands tend to be a little different than those used with other protocols, so let’s take a look at how EIGRP and split horizon interoperate.

R1 is our hub router, with R2 and R3 as the spokes. There are no subinterfaces, and each router is advertising a single loopback network using its router number for each octet. R1 will see both R2 and R3’s loopback network, but the spokes will not have a route to the other spoke’s loopback. “show ip route eigrp” verifies this.

R1#show ip route eigrp

2.0.0.0/32 is subnetted, 1 subnets

D 2.2.2.2 [90/2297856] via 172.12.123.2, 00:03:29, Serial0

3.0.0.0/32 is subnetted, 1 subnets

D 3.3.3.3 [90/2297856] via 172.12.123.3, 00:03:29, Serial0

R2#show ip route eigrp

1.0.0.0/32 is subnetted, 1 subnets

D 1.1.1.1 [90/2297856] via 172.12.123.1, 00:05:20, Serial0

R3#show ip route eigrp

1.0.0.0/32 is subnetted, 1 subnets

D 1.1.1.1 [90/2297856] via 172.12.123.1, 00:07:54, Serial0

EIGRP runs split horizon by default, making it impossible for R1 to forward an advertisement to R2 regarding R3’s loopback. Likewise, R1 cannot advertise R2’s loopback address to R3. We could configure two subinterfaces on R1 to resolve this issue, but here we’re going to disable split horizon instead.

R1(config)#int serial0

R1(config-if)#no ip split-horizon ?

eigrp Enhanced Interior Gateway Routing Protocol (EIGRP)


R1(config-if)#no ip split-horizon eigrp ?

<1-65535> Autonomous system number

R1(config-if)#no ip split-horizon eigrp 100

04:10:02: %DUAL-5-NBRCHANGE: IP-EIGRP 100: Neighbor 172.12.123.2 (Serial0) is down: split horizon changed

04:10:02: %DUAL-5-NBRCHANGE: IP-EIGRP 100: Neighbor 172.12.123.3 (Serial0) is down: split horizon changed

04:10:25: %DUAL-5-NBRCHANGE: IP-EIGRP 100: Neighbor 172.12.123.2 (Serial0) is up: new adjacency

04:10:37: %DUAL-5-NBRCHANGE: IP-EIGRP 100: Neighbor 172.12.123.3 (Serial0) is up: new adjacency

Note that disabling split horizon resulted in the EIGRP adjacencies being torn down. They came back up 20 – 35 seconds after being torn down according to the timestamps, but that’s a good detail to keep in mind!

The routing tables of each spoke should now show the loopback network configured on the remote spoke.

R2#show ip route eigrp

1.0.0.0/32 is subnetted, 1 subnets

D 1.1.1.1 [90/2297856] via 172.12.123.1, 00:00:02, Serial0

3.0.0.0/32 is subnetted, 1 subnets

D 3.3.3.3 [90/2809856] via 172.12.123.1, 00:00:02, Serial0

R3#show ip route eigrp

1.0.0.0/32 is subnetted, 1 subnets

D 1.1.1.1 [90/2297856] via 172.12.123.1, 00:00:02, Serial0

2.0.0.0/32 is subnetted, 1 subnets

D 2.2.2.2 [90/2809856] via 172.12.123.1, 00:00:02, Serial0

Be careful when disabling split horizon. In this scenario, R1 can and will advertise routes out Serial0 that were learned about on that interface in the first place, and that’s not always desirable. Split horizon is enabled by default for a reason, so be careful when disabling it!

How Does a MCSE Boot Camp Work?


One of the best methods of securing IT training, and preparing for your MCSE Certification examination is the boot camp. MCSE stands for Microsoft Certified System Engineer. The MSCE boot camp gives you the intensive training that you need to not only pass the examination, but also to handle the work afterwards. The boot camp concept takes its name from military basic training and although it does not resemble that in the discipline area, it certainly earns its name for its intensity.

A typical MCSE boot camp lasts around two weeks. The fee for the camp includes air transportation to the camp site, and lodging during the duration of the course. If air transportation and lodging are not needed, these expenses will be deducted from the cost. Meals are also included in these packages. Students will take up to seven certification examinations during the boot camp. The class room work will be directed toward preparation for each examination. Students will be working also on the actual hardware and software under the guidance of instructors who are experience in all Microsoft platforms. Most boot camps have 24/7 lab access available to the students.

There is a great deal of written material and computer training videos involved with the courses designed to prepare for the various Certification examinations. Many companies offer this material to students for home study. This is given as an alternative to the boot camp, and the advertising stresses the money savings for skipping the actual camp and doing the study and preparation at home. The costs of the boot camps are rather high, especially when they include transportation, lodging, and meals. Even though, in most cases, employers will pay for the cost of the camp, this is not always the case.

The Microsoft Certification boot camp has several benefits over home study and they justify the cost. Most camps offer success guarantees. If you fail an examination, the instructors are right there to correct any mistakes and identify the cause of failure. You will be prepared to retake the examination and get back on schedule. Since most boot camps have small classes and therefore a high instructor to student ratio, this individual attention is the key to successful completion of the Certification exams. Many of the camps have as high as 96% success rates, and many will allow credits to any student who does fail the complete the course. These credits may be used to retake the boot camp at a reduced rate at a later date.