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Is the Extra Layer Better? Layer 2 versus Layer 3 Networking

Is the Extra Layer Better? Layer 2 versus Layer 3 Networking

Switching technologies are crucial to network design, as they allow traffic to be sent only where it is needed in most cases, using fast hardware-based methods.

LAN switching uses different kinds of network switches. A Basic switch is marked as a Layer 2 Switch and is found in almost all Local Networks. Layer 3 switches are more advanced and expensive and become necessary in large enterprise networks.

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Layer 2 Networks
Layer 2 switching uses the media access control address from the host’s network interface cards to decide where to forward frames.  Layer 2 switching is hardware-based which means switches use an application-specific integrated circuit to make and sustain filter tables. Layer 2 networks are connected together using hubs, bridges and switches. None of these devices have to disassemble or reassemble data they only forward it. Because nothing is done to the data along the way, Layer 2 networks are often considered to be ‘faster’ than a Layer 3 network.

Layer 2 switches are frequently installed in the enterprise for high-speed connectivity between end stations at the data link Layer.

Layer 3 Networks
Layer 3 switches technically share much in common with traditional routers. A router works with IP addresses at Layer 3 of the model. Layer 3 networks are built to run on Layer 2 networks.
In an IP Layer 3 network, the IP portion of the datagram has to be read. This requires stripping off the data link Layer frame information. Once the protocol frame information is stripped, the IP datagram has to be reassembled. Once the IP datagram is reassembled, the hop count has to be decremented, the header checksum has to be recalculated, a lookup for routing must be made, and only then can the IP datagram be chopped back up and inserted into frames and transmitted to the next hop. All of this takes extra time.

Layer 3 devices restrict broadcast traffic such as ARP and DHCP broadcasts to the local network. This decreases overall traffic levels by allowing administrators to chop networks into smaller parts and restrict broadcasts to all that sub-network. This means there is a limit to the size of a Layer 2 network. A Layer 3 network, properly configured, can grow to any size.

How to Choose the Best Switches for Your Business?
The Cisco Catalyst 2950 and 2960 series are typical examples of Layer 2 switches and the Cisco Catalyst 3550, 3560, 3750, 3850, 4500 and 6500 series are good examples of Layer 3 switches.

Generally speaking, small networks can be built using just Layer 2 devices, but most corporate networks will have a mix of Layer 2 and Layer 3 switches. Dumb Layer 2 products are a cheap and easy way of providing connectivity to work groups while more intelligent Layer 3 switches enable departmental networks to be segmented and controlled with no loss of bandwidth.

If you are looking to upgrade your network and servers to be future-ready contact us today and we can create a solution based on your specific requirements and advise the most suitable technologies for you now and in the future.