Layer 3 Switches, What It Differ from Layer 2 Switches? - By: Irisdan

What is a Layer 3 Switch?
Layer 3 switches are hardware-based and optimized to transmit data as fast as Layer 2 switches, but Layer 3 switches use the IP address to make switching decisions, the same as a router. The 802.1Q VLAN of a Layer 2 switch allows network operators to configure and maintain networks more efficiently, but cross VLAN communication still relies on traditional Layer 3 routers. Both routers and Layer 3 switches use a routing protocol and routing table to determine the best path. However, compared to routers, which are usually software-based, Layer 3 switches are faster and less expensive due to the built-in switching hardware with optimized chips and full-wire speed IP frame forwarding performance suitable for connections between VLANs. Moxa's Layer 3 switches can be used to partition a large-scale LAN into multiple subnets for better network performance.
Static Routing
Instead of using a Layer 2 Ethernet switch MAC table, the EDS-828 series has a built-in IP routing table that supports the forwarding of IP frames. Network administrators must configure and maintain this IP routing table manually, and if any changes are made to the network topology, the administrator will need to reconfigure the routing table.

Routing Information Protocol (RIP)
In addition to static routing, the EDS-828 also has a built-in IP routing table that can be set up and updated dynamically by routing protocol. RIP is an often used routing protocol that uses the Bellman-Ford algorithm and "hop count" measurement to determine how packets should be routed from one network to another.

Open Shortest Path First (OSPF)
The EDS-828 series also supports OSPF, which uses "Link State" instead of "hop count" to determine the network route. OSPF is more complicated than RIP. However, compared to RIP, OSPF has faster network convergence and less network traffic. Both RIP and OSPF are usually referred to as Interior Gateway Protocols (IGP).

Static versus Dynamic
The EDS-828's built-in IP routing table can be updated and maintained both statically and dynamically. If the network is small and fixed, the network administrator can configure the IP routing table manually. However, if changes are made to the network topology, the network administrator must reconfigure the settings manually. If the network is extended or the network topology is changed frequently, dynamic routing can enhance network stability and reduce the time it takes to effect network convergence. Dynamic routing protocol allows devices to detect and respond to network changes automatically. In this case, network administrators do not need to reconfigure the settings when the network topology changes.

About the Author

Layer 3 switches act like a traditional router – it enables different network segments to be linked together. With this, data can be inter-networked from one network subnet to another. Prioritization of packets can be setup and the Layer 3 switch is intelligent enough to learn which routes are the best between the networks.

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