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My question is for small networks or perhaps large ones. When does it make sense to use a switch compared to a router implementation like NAT overloading? It seems to me, a networking novice, that both are being used inside the LAN vs. connecting networks to the Internet.

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Let's assume I have 10 computers on a private network. All ten need access to the internet. Nevermind VLANs and complex switches with routing capability. If I use NAT then all 10 machines will have private IPs and share a single public IP address. If I use a basic switch all 10 share a single public IP, but no private IP. Which method is better? Is it common to find networks that don't leverage private IPs? What is the benefit of using private IPs vs switching?

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  • So I can better understand your question, are you asking how to recognize when is it time to move your routing device from a layer 3 switch running a routing protocol to an actual router running a routing protocol?
    – Tom
    Commented May 25, 2017 at 1:24
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide and accept your own answer.
    – Ron Maupin ♦
    Commented Feb 19, 2018 at 4:15

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You are comparing apples and oranges (layer-2 vs. layer-3). You only use NAT if you really have no other option because of lack of IPv4 addresses, and that has nothing to do with layer-2 LAN connectivity.

Switching connects hosts at layer-2, while NAT is a kludge that is designed to extend IPv4 layer-3 addresses until IPv6 can become ubiquitous. NAT breaks the IP promise of unique addresses for every host and end-to-end connectivity.

Edit:

If I use a basic switch all 10 share a single public IP, but no private IP.

That sentence makes no sense. There would be no sharing of the single public IP address. If you connect a switch to the public Internet where you are getting only a single public IP address, then only one device connected to the switch will get the public IP address, but the other devices will not be able to communicate on the public Internet.

Understand that switches switch layer-2 frames on a layer-2 LAN, but routers route layer-3 packets between networks (LANs). Again, you are trying to compare apples and oranges. I think you need to learn more about the network layers and what they do. Each network layer is independent of the other network layers. For example, ethernet, at layer-2 can carry any number of layer-3 protocols (IPv4, IPX, IPv6, AppleTalk, etc.), while IPv4 at layer-3 can be carried by any number of layer-2 protocols (ethernet, Wi-Fi, token ring, PPP, frame relay, ATM, etc.). The protocols at one network layer simply do not care what protocols are used at the other layers.

If you want to connect hosts at layer-2, then you use a switch, but if you need to connect networks, you use routers.

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