Troubleshooting Q&A - April 13, 2005
Hubs, Switches, Routers ... What's the Difference?
Conversations concerning routers, switches and hubs can be a bit misleading because many people use the terms interchangeably. However, the functions of the three devices are all quite different from one another, even if at times they are all integrated into a single device.
By Ron Pacchiano
Q. I'm a bit of a newbie when it comes to computer networking, particularly when it comes to understanding the terminology used to describe network hardware. Specifically, the thing I'm most confused about at the moment involves routers, hubs and switches. Most of the technicians that I know have a tendency to use these names interchangeably. One minute they're talking about a switch. Two minutes later they're arguing over the router settings. Throughout all of this, though, they're still looking at only the one box. This leads me to believe that a hub, switch and a router are all the same thing, but I've been told that that's not the case. So could you please explain to me what the difference is between an Ethernet hub and/or switch and a broadband router? Thanks.
A. I can definitely appreciate your confusion on this topic. Today most routers have become something of a Swiss Army Knife, combining the features and functionality of a router and switch/hub into a single unit. So conversations regarding these devices can be a bit misleading especially to someone new to computer networking.
The functions of a router, hub and a switch are all quite different from one another, even if at times they are all integrated into a single device. Let's start with the hub and the switch since these two devices have similar roles on the network. Each serves as a central connection for all of your network equipment and handles a data type known as frames. Frames carry your data. When a frame is received, it is amplified and then transmitted on to the port of the destination PC. The big difference between these two devices is in the method in which frames are being delivered.
In a hub, a frame is passed along or "broadcast" to every one of its ports. It doesn't matter that the frame is only destined for one port. The hub has no way of distinguishing which port a frame should be sent to. Passing it along to every port ensures that it will reach its intended destination. This places a lot of traffic on the network and can lead to poor network response times.
Additionally, a 10/100Mbps hub must share its bandwidth with each and every one of its ports. So when only one PC is broadcasting, it will have access to the maximum available bandwidth. If, however, multiple PCs are broadcasting, then that bandwidth will need to be divided between all of those systems, which will degrade performance.
A switch, on the other hand, keeps a record of the MAC addresses of all the devices connected to it. With this information, a switch can identify which system is sitting on which port. So when a frame is received, it knows exactly which port to send it to, which significantly increasing network response times. And, unlike a Hub, a 10/100Mbps switch will allocate a full 10/100Mbps to each of its ports. So regardless of the number of PCs transmitting, users will always have access to the maximum amount of bandwidth. It's for these reasons why a switch is considered to be a much better choice then a hub.
Routers are completely different creatures. Where a hub or switch is concerned with transmitting frames, a router's job, as its name implies, is to route packets to other networks until that packet ultimately reaches its destination. One of the key features of a packet is that it not only contains data, but the destination address of where it's going.
A router is typically connected to at least two networks, commonly two LANs or WANs or a LAN and its ISP's network (ex. your pc or workgroup and EarthLink). Routers are located at gateways, the places where two or more networks connect. Using headers and forwarding tables, routers determine the best path for forwarding the packets. Router use protocols such as ICMP to communicate with each other and configure the best route between any two hosts.
Today, a wide variety of services are integrated into most broadband routers. A router will typically include a 4 - 8 port Ethernet switch (or hub) and a Network Address Translator (NAT). In addition, they usually include a Dynamic Host Configuration Protocol (DHCP) server, Domain Name Service (DNS) proxy server and a hardware firewall to protect the Local Area Network (LAN) from malicious intrusion from the Internet.
All routers have a Wide Area Network (WAN) Port that connects to a DSL or cable modem for broadband Internet service and the integrated switch allows users to easily create a LAN. This allows all the PCs on the LAN to have access to the Internet and Windows file and printer sharing services.
Some routers have a single WAN port and a single LAN port and are designed to connect an existing LAN hub or switch to a WAN. Ethernet switches and hubs can be connected to a router with multiple PC ports to expand a LAN. Depending on the capabilities (kinds of available ports) of the router and the switches or hubs, the connection between the router and switches/hubs may require either straight-thru or crossover (null-modem) cables. Some routers even have USB ports, and more commonly, wireless access points built into them.
Some of the more high-end or business class routers will also incorporate a serial port that can be connected to an external dial-up modem (useful as a backup in the event that the primary broadband connection goes down) and a built in LAN printer server and printer port.
Besides the inherent protection features provided by the NAT, many routers will also have a built-in, configurable, hardware-based firewall. Firewall capabilities can range from the very basic to quite sophisticated. Among the capabilities found on leading routers are those that permit configuring TCP/UDP ports for games, chat services, and the like, on the LAN behind the firewall. (More on port assignments.)
So, in short, a hub glues together an Ethernet network segment, a switch can connect multiple Ethernet segments more efficiently and a router can do those functions plus route TCP/IP packets between multiple LANs and/or WANs; and much more.
I hope this helps.
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