As soon as at least two segments appear on the local network (for example: a user segment, a server segment), it becomes necessary to use routing equipment that operates at the third level of the OSI model. In this case, the question may arise: “What to use? Layer 3 switch or router? What is the difference, what are the differences? ” Let’s try to figure it out.
Initially, these two devices have different purposes.
A L3 switch is primarily a device for a local area network (LAN). Those. this switch must route traffic on the local network between existing segments. It is usually used at the Distribution Layer in a hierarchical network model.
The router is designed to connect a local area network (LAN) to the WAN (Wide Area Network), i.e. It routes traffic to the outside world (the Internet, branches, remote employees) and vice versa.
The question may arise: “Why do we need a layer 3 switch if its functions can be performed by a router?”
Without going into details, the third-level switch can be compared to a very fast router. He also knows how to work with dynamic routing protocols (OSPF, RIP) and is absolutely compatible with a conventional router. You can configure access lists (so-called access lists) and much more.
The answer lies in performance and price. The fact is that modern Layer 3 switches outperform routers by tens or even hundreds of times in performance. This is due to the use of specialized chipset (ASIC) switches. Routing (packet processing) occurs at the hardware level, and software support remains for procedures that are not directly related to traffic processing: calculation of routing tables, access lists, etc.