Network Router Vs Layer 3 Switch, is layer 3 switch is eliminating the requirement of Network Router ?

Network routers and Layer 3 switches both operate at the OSI model's Layer 3, handling IP routing, but they serve distinct roles in networking. A router is designed for connecting disparate networks, managing wide area network (WAN) links, performing network address translation (NAT), firewalling, and advanced features like VPN tunnels or quality of service (QoS) prioritization. It excels in environments requiring robust security and protocol support, such as linking branch offices to the internet or data centers.
In contrast, a Layer 3 switch combines the speed of Layer 2 switching with basic Layer 3 routing, ideal for high-performance local area networks (LANs) where fast inter-VLAN routing is needed without the overhead of full routing protocols. However, it does not eliminate the need for a router, as switches typically lack WAN interfaces, deep packet inspection, or complex policy-based routing found in routers. For instance, in a corporate setup, a Layer 3 switch might route traffic within a building, while a router handles external connectivity.
Examples from different OEMs include Cisco's Catalyst 9300 as a Layer 3 switch and ISR 4000 as a router; Juniper's EX4600 switch versus MX series router; and Arista's 7050SX switch compared to its 7200 router line. Ultimately, they complement each other for scalable architectures.
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