How Do Multiple Ethernet Switches Connect?
When one switch cannot meet the number of ports and a specific functional requirement, usually users will connect multiple Ethernet switches together, so how to connect multiple Ethernet switches together during network deployment? Three common types of connections are currently available: cascading, stacking and clustering. This article aims to clarify these three techniques and the best way to connect the switches among them.
Connecting Multiple Ethernet Switches with Cascading
Cascading is the traditional method of connecting multiple Ethernet switches. By cascading multiple switches together, it gives users more available ports to connect to other devices, where all ports can be independently configured and managed within the group. Switches are generally cascaded to each other through common ports, but some switches can also provide dedicated cascade ports. Depending on the requirements, multiple switches can be cascaded in a variety of ways. Among them, daisy-chain and star are the two most common topologies in switch cascade networks.
Daiku-chain Topology - Switch Cascading
As the name suggests, a daisy-chain topology is one in which switches are connected in series, like the petals of a daisy. This is the easiest way to connect multiple switches in a network. The switch cascade with daisy chain topology can be linear, as in Figure 1 below, where the switches at both ends are unconnected (simply put, A-B-C-D) and there is no loop; at the same time, it can also be looped, as in Figure 2 below, where the switches at both ends are connected (that is, A-B-C-D-E-F-A) to form a loop.
For cascading less than three Ethernet switches using linear daisy-chain topology is possible because there are no loops, but due to the lack of redundancy, it is flawed in terms of switch failures and if one of the Ethernet switches fails, the other Ethernet switches will be dragged down as well. Typically, the linear daisy-chain topology is less flexible and resembles an electrical series circuit, where the outage of all one of them affects the other connected devices.
For cascading more than three Ethernet switches a ring daisy-chain topology is preferable because it allows bi-directional transmission. If a link in the ring breaks, data can be transmitted through the reverse transmission path, thus ensuring that all Ethernet switches can be connected even in the event of a single link failure. However, in a ring daisy-chain topology, Ethernet switches will inevitably generate loops, which can cause broadcast storms and network congestion. Therefore, it is desirable to ensure that all connected Ethernet switches can support relevant protocols such as STP in order to solve the loop problem.
In a star topology, all access switches in the network can be connected to the core switch in a point-to-point manner, and then the core switch transmits data to the destination. This means that the communication between two access switches in a star network must be controlled by the core switch. Therefore, the core switch needs to be more powerful than the access switch.
Currently, switch cascading in a star topology is widely used to connect multiple Gigabit switches. Usually, when connecting gigabit switches using star topology, a powerful switch (e.g. 10G switch) can act as a core switch and then connect to an access switch (i.e. gigabit switch). No loops are created when switches are cascaded using a star topology, and all access switches are relatively close to the core switches.
Connecting Multiple Ethernet Switches with Stacking
Stacking is the process of forming multiple switches into a single unit, resulting in greater port density and higher performance, but not all switches can support stacking capabilities. When multiple switches are stacked together they will form a stacking unit, where the port density of the stacking unit is the sum of all ports and the bandwidth, thus effectively improving network connectivity.
Connecting Multiple Ethernet Switches with Clustering
Clustering is the management of multiple interconnected switches as one logical device, where the interconnections can be cascaded or stacked. Simply put, cascading and stacking are prerequisites for achieving clustering, and clustering is the purpose of cascading and stacking. In a cluster, there is usually only one switch with a management role (i.e., the command switch) that can manage several other switches. In the network, these switches only need one IP address (used by the command switch), which can effectively save valuable IP address resources. At the same time, under the same management of the command switch, multiple switches in the cluster work together, reducing the management intensity to a large extent.
As you can see above, cascading (daisy chain topology and star topology), stacking and clustering are the three ways to connect multiple Ethernet switches. In fact, cascading, stacking and clustering all have their own advantages and disadvantages, so the choice of which way to connect multiple switches should depend on your actual application.