Quick Answer: The three main components of a network are switches, routers, and firewalls. Switches keep devices talking, routers connect networks to each other (and the internet), and firewalls act as security guards that keep out unwanted traffic. For enterprise network architects and senior infrastructure engineers, determining where Layer 3 routing logic should reside—on the core switch or the Next-Generation Firewall (NGFW)—is a foundational design decision. It can determine which traffic is allowed to pass and which needs to be blocked according to a predefined set of security rules. I won't have a firewall as a core router on the DC, but for a office why not?, you deploy an HA pair and they can do the ngfw, routing, sd wan or bgp (I won't do full tables), user ssl vpn and ipsec site 2 site, ids, even wifi controller. Routing Table: A router's routing table contains all known routes, including static routes, dynamic routes, and directly connected routes.
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