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As a CCNA candidate, you most likely involve some history in PC hardware and workstation support. You are already knowledgeable about loopback interfaces, particularly 127.0.0.1, the loopback address given to a PC, In that case.

When you're learning all about different physical interfaces for your CCNA test - serial, ethernet, and BRI, among others - there is one logical interface you need to find out about, and that is - you thought it! - the loopback interface.

we use loopback interfaces on routers and switches in the first place what is not as immediately evident is. Most of the Cisco router features that may use loopbacks are intermediate and advanced features that you'll find out about in your CCNP and CCIE studies, but these features all get back to one basic concept: If the loopback interface on a is down, that means the router is unavailable as a whole.

In contrast, a interface being down doesn't mean the modem itself has gone out of commission. A router's ethernet port may drop, however the other physical interfaces on that router are still operational. Since a loopback interface is sensible, there is nothing physical that may make a mistake with it.

As I mentioned, you'll learn different Cisco router and switch functions that utilize loopback interfaces as you climb the Cisco certification hierarchy. There's one myth about Cisco loopback interfaces that you want to obtain clear on today, although. Youre probably familiar with loopback interfaces on a PC, and could even realize that the target range 127.0.0.0 is reserved for loopback handling.

Note that this reserved target variety doesn't apply to loopbacks on Cisco devices, however. If you make an effort to assign an address from this variety 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 really a legitimate host address - 127.0.0.2

R1( config-if )#ip target 127.1.1.1 255.255.255.0

Not really a valid host address - 127.1.1.1

The product range 127.0.0.0 is reserved for host loopbacks (such as PCs), perhaps not hubs or switches. The absolute most widely used target out of this variety is 127.0.0.1 if you cant ping that on a, that means you cant ping your self, which means theres a challenge with the TCP/IP mount itself.

Hold these details in mind on the exam and in the workplace, and youre on the right path to CCNA exam success! ccna certification