With all modern devices, some of the terms can be confusing. Almost everyone has heard of the term router, but what does it really mean? Is your router just a router or can it also be a switch, access point, and gateway?
In the past, each term above usually referred to a single device performing one function. This is no longer the case these days. Your “modem” from your ISP is likely a modem, router, switch, and access point at the same time. You don’t need to have a generic device, as I’ll explain later, although some ISPs insist on this.
In this article, I will try to explain the concept of each of these terms without getting too technical. I’ll first talk about the difference between switches and hubs, since both of these devices are in the same category. Next, we’ll talk about routers and how they differ from switches and hubs. Finally, we’ll talk about modems and other networking terms like access points and gateways.
Switches versus hubs
A hub is an outdated device that you would never want to buy these days. It looks the same as a switch but works differently internally. You connect devices to a hub using an Ethernet cable, and any signal sent from the device to the hub is simply echoed on all other ports connected to the hub.
Hubs are considered Layer 1 (physical) devices, while switches are placed on Layer 2 (data link). This is the difference between hubs and switches. The OSI data link layer deals with MAC addresses, and switches look at MAC addresses when processing an incoming frame on a port.
A frame is a data type that is used to transfer data across all network devices. Don’t worry about the technical details, just know that it contains source and destination MAC addresses as well as source and destination IP addresses within the frame. The portion of the frame containing the source / destination IP addresses is called a packet.
Instead of blindly forwarding all the frames it receives on one port to all other ports on the device, the switch creates an initial MAC address table and then forwards the frame to the port with the correct destination MAC address. This greatly reduces the amount of traffic on the network because there is a direct link between the two devices, rather than a public link.
When using hubs, the more devices you connect to the hub, the more conflicts there will be on the network. Collision means that two computers or devices are sending data at the same time, and the signals physically collide before reaching their destination. This often happens on hubs because all traffic going to each port is repeated to all other ports.
There are no conflicts with switches, because only two devices that exchange data will send data back and forth. The bandwidth is not being used by other ports.
For the same reason, the hub is half duplex and the switch is full duplex. The more devices in a hub, the more bandwidth needs to be shared, and hence the network becomes slower. On switches, bandwidth should not be shared and all ports are operating at full speed.
Router vs modem
Routers operate at layer 3 (network) of the OSI model, which deals with IP addresses. While MAC addresses are used to move frames from one device to another, directly connected device, IP addresses are used to route packets across the Internet.
A router is a device that connects networks and routes traffic between them. At home, this usually means that the router connects the internal LAN to the ISP’s network. This can be done in several ways. A router can be connected to your modem at one end (ISP) and to a switch at the other end (LAN). If you have a combo modem / router, then one end will connect to your ISP and the other will either to the switch if Ethernet is used, or just Wi-Fi if the device supports it.
Above is a typical router (technically above is a wireless router). The internet port will connect to your modem, and the rest of the ports are switch ports. A router almost always has a built-in switch. The modem will connect to your ISP via a telephone line (for DSL), cable or fiber optic (ONT).
Above is a typical cable modem. It has one coaxial port for a cable connection coming from your ISP and one Ethernet port that you can connect to an Internet port on your router. It is always best to use two different devices for your modem and router whenever possible.
A wireless router simply lets you use a wired connection with whatever wireless devices you have. Most modern routers are wireless routers that also include multiple wired ports.
Wireless router versus wireless access point
Now let’s talk about wireless routers and wireless access points. A wireless access point is a device that allows wireless devices to connect to an existing wired network by passing traffic between two networks. The reason these two terms are so confusing is because a wireless router is essentially a router and a wireless access point combined.
However, the wireless access point cannot be a wireless router. A standalone wireless access point will have an Ethernet cable going to the router and convert the wired signal to wireless. It will not route packets from the LAN to another network or to the Internet like a normal router.
Wireless access points are typically used in enterprises or large public places where multiple wireless stations are required to be connected together to form a single network. Wireless routers usually have built-in firewalls, but wireless access points do not.
Other networking terms
Another very common term you’ll hear is default gateway. So what’s the default gateway? Basically, it is a device that connects your local network to the outside world. This is usually the last router on your local network.
On a home network, the default gateway will most likely be your wireless router, because anytime you need to communicate with a device outside of your network, the router is the device that is connected to your modem. Note that a default gateway is not required to communicate with other devices on your local network. Default gateways are only used when communicating with remote networks, such as the Internet.
Hopefully this clears up some of the mystery of all these networking terms. This is a simplified overview, but enough for you to explain to someone else. Enjoy!