Cause and reason of Looping, and solution

In this session, we will learn about looping that occurs in the network.

 

Let's find out in detail why looping occurs, what problems occur when looping occurs, and how to solve looping.

 

 

1. What is  looping?

 

 

To study spanning tree, you must first understand Loop.

 

It would be meaningful to learn the protocol to prevent looping when you know why it occurs. Then what is looping? Let's see why it happens.

 

 

What is Looping?

: It refers to a state in which data cannot be easily and infinitely transmitted on a network.

 

< looping >

 

 

 

If you look at the picture above, you can see Switch A & Switch C.

 

By default, the switch floods packets to the rest of the ports except the ports that came in. Switch A and C have two cables connected, right?

 

(We usually connect only one, but we explain by connecting two to create a structure that causes loops.) Let's say cable number one and cable number two.

 

 

 

The PC on Switch A sends packets to the PC on Switch C. Switch A then sends packets to the rest of the ports except the ports to which the PC is connected.

 

 

The packet is sent to cable 1, and the packet is sent to cable 2. In Switch C, packets coming through cable 1 will flood the rest of the ports, and in Switch C, packets coming through cable 2 will flood the rest of the ports.

(If you draw and take notes with a pencil, you will understand quickly.)

 

 

Then, the packet that came into cable 1 will be sent back to cable 2, and the packet that came into cable 2 will be sent back to port 1 and 2 indefinitely.

 

If this process is repeated, a looping occurs in which once a broadcast packet continues to circle the network through both switches.

 

 

 

 

This looping will prevent other data from being transferred. So the network can't do anything. It's not visible to us, but the data will be spinning at a tremendous speed through both ports.

 

 

The switch itself is also processing this packet, causing the CPU to rise indefinitely, leaving the switch itself unable to do anything else.

 

 

The switch is dead, so of course the network won't work.~ This site is a mess. The internet won't work. This is called Looping.

 

 

 

※ Problems Caused by Looping

 

- Switches continue to propagate broadcast traffic over and over again, and switches will consume a lot of CPU resources to handle it, consuming all of their resources, eventually causing the entire network to go down.

 

 

When you are a field engineer, one of the common problems is this loop problem.

 

These days, STP is basically enabled on the switch, but there are many switches that are disabled.

 

 

As a result, the loop structure is made by misconnecting the cable as described above, and then the looping occurs, causing the site to fail.

 

 

So, you have to study STP, and before you do STP, why does this Looping happen? Please remember what kind of problems occur when they occur.

 

I've found out why Looping occurs, but it's easier than you think, right?

 

 

If you understand the picture above correctly, you will understand it without much trouble even if you look at the other application configurations.

 

 

What is Virtual LAN (VLAN)?

 

VLAN Tag & Untag Concepts and Differences

 

 

저의 글을 읽어 주셔서 감사합니다. 오늘도 즐거운 하루 보내세요.