A network switch is a device that connects other devices together in a computer network. Here we are specifically discussing computer networks, but of course there are switches in other fields too. All operate in similar ways, by connecting different devices through their physical ports. Most computer network switches fall into one of two categories, data link layer and multilayer switches. The former use the MAC addresses of devices to direct traffic to the appropriate destination, while the latter can also use IP addresses.
Functionally, they do the same job: ensuring that a packet from a source reaches the right destination. This role must not be confined to a single network as switches can also connect multiple networks.
Even non Ethernet-based network types, such as Token Ring or Fibre Channel can be united with a switch, a multilayer switch in such cases.
Switches are extremely common in networks, playing the role of the backbone of network performance and reliability. It is therefore natural to think of implementing a switch monitoring system to ensure the network’s overall stability. The monitoring of switches will allow the ‘taking the pulse’ of how well all of the switches in your network function, or not, and alert you of any malfunctions.
Switch ports are physical connections to which devices can be attached, and which connect to the network the switch operates on. In the vast majority of enterprise networks, these ports are Ethernet ones, the most common also in consumer-grade devices. Switches have multiple switch ports, on a variable number that goes from fewer than a dozen to multiples of ten. When more ports are needed, more switches can be added and possibly interconnected.
These ports are those that are monitored when implementing port monitoring, the subcategory of switch monitoring that takes care of checking how well the ports, not just the switches, work. As the actual traffic goes through switch ports, these cannot be ignored in the context of monitoring your infrastructure.
There are many types of switch port, differing in the supported network technologies, network architecture’s role, and functionalities. Ethernet switches will have RJ45 connectors, while Token Ring switches have STP connectors. The family of SFP connectors is to be found on switches that support Gigabit Ethernet or Fibre Channel networks. Similarly, for other network technologies, switch ports will be physically different. Switches supporting more than one type of connector are common though.
Depending on the switch port’s role, we have access, trunk, and hybrid ports. Access ports give devices access to a single network, while trunk ports connect different networks. Hybrid ports play both roles. These roles are independent of a switch port’s physical form.
Furthermore, there are a few special types of switch ports with specific functionalities. A stack port is one used to connect other switches of the same model, brand, and switch software version. These are useful to increase the port capacity of a network as all the thus stacked switches will have a usable port number equal to the sum of the combined switches. PoE (Power over Ethernet) switch ports are capable of carrying data and power on a single port, saving physical space on the rear of switch hardware.
All of these various ports can be regularly checked in network port monitoring, with their collected metrics of course differing according to the ports’ roles and network technology.