Pros and cons
In: Technology
A prevention loop on an Ethernet switch, often called Spanning Tree Protocol (STP), stops network loops which can cause broadcasts to endlessly circulate, clogging the network. The main pro is network stability and prevention of broadcast storms. The con is potential added latency or downtime as the network recalibrates after changes.
When a computer doesn’t know where the server that it needs is, it screams for help, and the first qualified server to hear the cry for help answers. This is called a “Broadcast”. A broadcast message + a loop = broadcast storm. Where the broadcast message loops recursively. It doubles and doubles and doubles till the entire network is brought to a grinding halt.
If you have a simple ethernet switch. and you plug one end of a cable into a port, and the other end of that same cable into another port on the same switch, that is a loop.
Often times it is never THAT simple. loops can be created in many ways.
Someone could route the traffic between two ports improperly.
That lawyer on the 12th floor could plug both the in and out of his IP phone phone into the wall.
You could have a whole family trees worth of network devices only to have a spot of incest in the 4th generation.
Loop prevention allows for human error while keeping the network relatively stable. You still want to track down and remove loops whenever possible.
A prevention loop runs what’s called Spanning Tree Protocol or STP.
An important part of network traffic is broadcasts, packets that are sent to every device on a network. When such a packet enters a switch it is rebroadcast to every port.
If you create a loop by plugging an ethernet cable from a switch back into the same switch these broadcast packets will start to endlessly circulate. They will leave the ports that are looped and come back in again and be rebroadcast over and over again.
This uses up more and more CPU, memory, and bandwidth on the network until it switch stops functioning either crashing dropping traffic.
Spanning Tree works by detecting such loops and shutting down one of the ports before it can do any damage.
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