Spanning Tree Protocol

Spanning Tree Protocol (STP) is a Layer 2 protocol that runs on bridges and switches. The specification for STP is IEEE 802.1D. The main purpose of STP is to ensure that you do not create loops when you have redundant paths in your network. Loops are deadly to a network. When too many computers try to send at the same time, overall network performance is affected and can bring all traffic to a near halt. That's why STP is used to solve this issue. 

A bridge looks at the destination address and, based on its understanding of which computers are on which segments, forwards the data on the right path via the correct outgoing port. Network segmentation and bridging can reduce the amount of competition for a network path by half  assuming each segment has the same number of computers. As a result, the network is much less likely to come to a halt. When STP is enabled, each bridge learns which computers are on which segment by sending a first-time message to network segments. Through this process, the bridge discovers the computers' locations and records the details in a table. When subsequent messages are sent, the bridge uses the table to determine which segment to forward them to. Enabling the bridge to learn about the network on its own is known as transparent bridging, a process that eliminates the need for an administrator to set up bridging manually. 

Spanning Tree comes into play by only allowing a singular path to destinations when having multiple (redundant) links such as this. In a STP environment, the switches exchange information among themselves using bridge protocol data units (BPDU) and will then listen in on all ports for this BPDU message. Once a bridge is turned on, it automatically assumes that it is the root bridge in the STP tree. The STP software chooses a root bridge and calculates all paths from the lower bridges back to itself. In the event of hardware failure of a root bridge in the redundant environment, a new root is elected and port paths would be recalculated.

With multiple uplinks, STP is a must in our switched environment to provide multiple redundancies in case one goes down, another link is there to takes it place within a matter of seconds. At this stage in our continuously growing network topology, there’s virtually no way you’ll ever lose the connection to your dedicated server. That is of course you don’t reboot the server itself, then that’ll be your expected momentary loss of connectivity.