Layers 2 switch and layer 3 switch are adopted in the Open System Interconnect OSI model, which is a reference model for describing and explaining network communications. The OSI model has seven layers: application layer, presentation layer, session layer, transport layer, network layer, data link layer and physical layer, among which layer 2 and layer 3 refer to the data link layer and network layer respectively, and the switches working in these layers are called layer 2 switch and layer 3 switch.
The layer 2 and Layer 3 differs mainly in the routing function. Layer 3 switch , or multilayer switch, can do all the job of a layer 2 switch and additional static routing and dynamic routing as well. Other than routing packets, layer 3 switches also include functions that require to understand the IP address information of data entering the switch, such as tagging VLAN traffic based on IP address instead of manually configuring a port.
Layer 3 switches are increased in power and security as demanded. When lingering between Layer 2 and Layer 3 switches, you should think about where it will be used. If you have a pure Layer 2 domain, you can simply go for Layer 2 switch. A pure Layer 2 domain is where the hosts are connected, so a Layer 2 switch will work fine there. This is usually called access layer in a network topology. It can support routing protocols, inspect incoming packets, and can even make routing decisions based on the source and destination addresses.
This is how a layer 3 switch acts as both a switch and a router. Often referred to as a multilayer switch, a layer 3 switch adds a ton of flexibility to a network. There is a ton of confusion about the use of a layer 3 switch because in a traditional setup, routers operate at layer 3 of the OSI model while switches operate at layer 2.
So, how does this layer 3 switch fit into this model? Originally, layer 3 switches were conceived to improve routing performance on large networks, especially corporate intranets. Layer 2 switches work well when there is low to medium traffic in VLANs. But these switches would hang when traffic increased. One option was to use a router instead of a switch, but then routers are slower than switches, so this could lead to slower performance.
To overcome this downside, researchers thought about implementing a router within a switch. Though technically feasible, it was not the ideal option because layer 2 switches operate only on the Ethernet MAC frame while layer 3 handles multiple routing protocols.
Researchers felt this was too complicated, so they came up with the idea of a layer 3 switches that acted as routers with fast forwarding done through the underlying hardware.
This is why the main difference between layer 3 switches and routers lies in the hardware. Just like any product, a layer 3 switch also comes with its own share of downsides.
Cost is one of the major downsides to a layer 3 switch. It costs much more than a traditional switch and configuring and administering these switches also requires more effort.
So, an organization should be ready to spend extra resources to set up layer 3 switches. Layer 3 switches are most applicable only for large intranet environments with many device subnets and traffic. Homes and small organizations do not need these switches. Lack of WAN functionality is another major disadvantage with layer 3 switches. When compared to layer 2 switching, layer 3 routing is relatively slower.
This can be an issue when you want to span VLAN over multiple switches for supporting multiple tenants and virtualization. This limitation means you have to plan well to avoid one LAN from using multiple switches. Now comes the big question: Do you need a layer 3 switch at all for your network? Well, it depends on your network configuration and its size. If you answered yes to one or more of the above questions, you sure need a layer 3 switch for improved performance.
In all other cases, it is optional. Layer 3 switches act as both switches and routers. But within VLANs, it gives you multiple options to manage your bandwidth efficiently. Physical layer. Data Link layer. Network layer. Transport layer. Application layer. Network Security. Computer Network Quizes.
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