Ethernet switches provide a variety of benefits for networks. They can be found in various configurations to accommodate any business’s needs. From unmanaged network switches that offer plug-and-play connectivity to Gigabit Ethernet switches that provide faster connections than wireless options.
How do ethernet switches work? The ethernet switch operates at the data link layer, where streams of 1s and 0s become packets. These packets contain key identifying information, such as the source and destination of the communication between devices.
Transparent Bridging
A transparent bridge is a layer-2 device that forwards data frames without altering the frame’s original format. It is a common type of bridge in most ethernet/IEEE 802.3 networks. It can learn about LAN segment topology and route data between different LAN segments by listening to MAC addresses transmitted over the network. This type of bridging technique reduces network collisions and improves performance. It also enables devices that use different higher-layer packet formats (LLC and Ethernet) to communicate with each other.
When a frame arrives on the bridge, it examines the destination MAC address and compares it with its MAC address-forwarding table. If the MAC address is in the forwarding table, the bridge will transmit the data frame to the destination end system over one of its ports.
This basic bridging process works well if the overall network is loops-free. However, some network topologies have loops that generate broadcast radiation and cause problems. To solve this problem, a network designer implements a protocol.
Bandwidth Control
Unlike Ethernet hubs, which retransmit every packet out of every port except where it was received (a practice called cut-through forwarding), switches can identify specific destination addresses. This allows them to more smoothly select how they filter and forward traffic between ports, making it easier to set up new endpoints in the network without disrupting existing users.
To do this, Ethernet switches operate at the data link layer (layer 2 of the OSI model), separating network segments into unique collision domains for each switch port. Each frame a switch receives is assigned a 48-bit media access control (MAC) address. The software in a switch continuously updates and maintains a database of these MAC addresses. When a frame arrives at a switch, the software looks up this MAC address in its database and decides whether to forward the frame to the corresponding device.
To further streamline this process, switches also participate in a distributed algorithm called spanning tree protocol. This involves each switch electing a root switch and determining the shortest path to the root based on the links’ weights.
Port Mirroring
Port mirroring enables you to monitor network traffic on switches without breaking encryption or exposing your data to sniffers. When enabled on a switch, each packet that arrives on a mirrored port is duplicated and sent to a dedicated monitoring port. A separate network analyzer or intrusion detection system (IDS) can then analyze this traffic.
To implement this feature, you must configure the switch to create a mirror of all the network traffic it sees. This can be done using a spanning-tree command with a port-mirroring statement. Then, it would help if you designated which ports on the switch should be mirrored, including the source and destination ports.
Suppose a switch is configured to mirror both incoming and outgoing network packets. In that case, it can be used to identify potential hardware or software issues that may be to blame for sluggish network performance. However, it’s important to remember that capturing duplicated packets on all switch ports can overwhelm them and cause a loss of switching capacity. For this reason, it is recommended to use other methods of gathering and analyzing network traffic before turning to port mirroring.
VLANs
Virtual (software-configured) local area networks can simplify network administration depending on your network needs. They’re also a great way to segment your network without undertaking an expensive project like micro-segmentation. By dividing your network into multiple VLANs, you can isolate different user groups based on your chosen criteria.
On a normal LAN, devices send frequent broadcasts to get IP addresses, find resources, and communicate with one another. These messages can clog up your bandwidth and slow down your network. VLANs solve this problem by separating broadcast traffic into logically separate segments.
A VLAN tag is an identifier in an Ethernet frame that tells the switch which VLAN it belongs to. The tag is inserted between the source address and the type/length fields in an Ethernet frame. The switch knows which ports are assigned to which VLANs to route the packet to its destination. VLANs work only on manageable Ethernet switches, and they’re a switch-only feature. Devices in different VLANs can only communicate directly if they connect through a router.
MAC Address Management
Every network device, whether a computer or printer, has a unique Media Access Control (MAC) address that uniquely identifies the equipment. It’s like the digital equivalent of a house number and allows network devices to communicate with each other over Ethernet cables.
MAC addresses are burned into the network interface card (NIC) hardware during manufacturing and cannot be changed. The MAC address is split into six octets, each with eight bits. The first octet identifies the manufacturer and vendor, while the remaining octets identify the specific device.
When a device wants to communicate with another on the same local network, it constructs a data frame by including both the source and destination MAC addresses. The destination MAC address is then used to deliver the frame to the intended device.
MAC address management ensures only authorized devices can connect to the network. It is important to update the list of permitted MAC addresses regularly to avoid connectivity issues and streamline network access.