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As a CCNA candidate, you most likely have some background in PC hardware and workstation support. If so, you’re already familiar with loopback interfaces, particularly 127.0.0.1, the loopback address assigned to a PC.

When you’re learning all about the different physical interfaces for your CCNA exam – serial, ethernet, and BRI, among others – there’s one logical interface you need to know about, and that is – you guessed it! – the loopback interface.

What isn’t as immediately apparent is why we use loopback interfaces on routers and switches to begin with. Many of the Cisco router features that can use loopbacks are intermediate and advanced features that you’ll learn about in your CCNP and CCIE studies, but these features all come back to one basic concept: If the loopback interface on a router is down, that means the router is unavailable as a whole.

In contrast, a physical interface being down does not mean the router itself is out of commission. A router’s ethernet port can go down, but the other physical interfaces on that router are still operational. Since a loopback interface is logical, there’s nothing physical that can go wrong with it.

As I mentioned, you’ll learn different Cisco router and switch features that utilize loopback interfaces as you climb the Cisco certification ladder. There’s one misconception about Cisco loopback interfaces that you want to get clear on now, though. You’re probably familiar with loopback interfaces on a PC, and may even know that the address range 127.0.0.0 is reserved for loopback addressing.

Note that this reserved address range does not apply to loopbacks on Cisco devices, however. If you attempt to assign an address from this range to a Cisco loopback interface, you get this result:

R1#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R1(config)#interface loopback0

R1(config-if)#ip address 127.0.0.2 255.255.255.0

Not a valid host address – 127.0.0.2

R1(config-if)#ip address 127.1.1.1 255.255.255.0

Not a valid host address – 127.1.1.1

The range 127.0.0.0 is reserved for host loopbacks (such as PCs), not routers or switches. The most commonly used address from this range is 127.0.0.1 – if you can’t ping that on a workstation, that means you can’t ping yourself, which means there’s a problem with the TCP/IP install itself.

Keep these details in mind on the exam and in the workplace, and you’re on your way to CCNA exam success!

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To earn your CCNP, you’ve got to pass some very rigorous Cisco exams, and you also need to know the rules regarding this important certification. In this article, I’ll answer some of the most commonly asked questions regarding the CCNP.

Q: What exams do I need to pass to get my CCNP?

A: You have two options, a three-exam path and a four-exam path. Currently, the four-exam path consists of rigorous exams on advanced routing techniques (BSCI), advanced switching (BCMSN), remote access methods (BCRAN), and advanced troubleshooting techniques (CIT). The three-exam path combines the BCMSN and BSCI exams into a single exam, the Composite exam.

Q: Do I have to take them in any order?

A: No, the order is up to the candidate. Most CCNP candidates take the BSCI exam first and the CIT exam last, but again this is up to the candidate.

Q: What else do I have to do to get the CCNP?

A: You must earn your CCNA before you can be CCNP certified (as well as passing the exams, of course).

Q: Is there a recertification requirement?

A: Cisco CCNP certifications are valid for three years. During that time, you must either pass the Composite exam, the BSCI and BCMSN exams, or pass any CCIE written exam.

Q: What if I don’t recertify within the three-year period?

A: You must then meet whatever CCNP requirements there are at that time, from the beginning. It’s easier to make sure you recertify!

Becoming CCNP certified is a great boost to your career and your confidence, and as with any Cisco certification, it’s up to you to stay current with the CCNA and CCNP requirements. Visit the Career Certification section of Cisco’s website regularly to learn about the program’s requirements and changes.