What's the difference between a hub, switch and a router?


Everything sent through an ethernet network is basically cut into small bits of data known as packets. The computer wishing to send information gives the packets an address, and sends them down the cable.


If the packet comes to a hub, then the hub copies the packet and sends it to every other port it has. Once one of the packets gets to the proper destination, the intended recipient sees their address on the packet and accepts it. Those that do not see their address on a packet, discard. With a hub, if systems try to send on the line at the same time then a data collision occurs and the packets must be resubmitted.


A switch is a bit smarter. It learns the addresses of the individual systems. When a packet comes to it, the switch takes a look at the address on it and sends the packet to it's proper destination without sending it to everyone else too. Due to these improvements over the hub, the switch often performs better where high network throughput is desired.


A router is the smartest and most complicated of the bunch. A router is used to interconnect multiple networks. The Internet is literally Internetwork -- a network of networks. Internet router’s work on IP addresses to determine how best to interconnect the sender to the destination. A router allows multiple devices to access one point of connection (such as an ADSL connection if the router's an ADSL router with a built-in ADSL modem, an uplink to the Internet if being used on a network, or another computer being used as an upstream proxy server). Routers commonly have DHCP servers installed, to provide connected devices with an INTERNAL ONLY IP address on a private subnet range. This means that whilst the internet will see only one requests from one IP address (the outward IP address of the router's ethernet adaptor / adsl modem), the router's routing table, combined with the abillities of the DHCP server, can cope with multiple requests to various sources (web sites, gaming servers etc), routed through the one external connection, but separated out and correctly distributed to the various connected devices.



An access point is a wireless version of a switch - it's a much simpler device, similar in function to a router, but with no DHCP server - it merely acts as a pass-through for multiple devices to transparently connect to (and share) a single uplink or other connection. As switches contain no DHCP server, they can be connected to a router to provide a) extra connectivity, and b) further network availability reach for wireless devices.


All "wireless" routers have an Access Point built into the router. This is what makes it a "wireless" router. There are some models that are just wireless Access Points without router functionality. These will only work if your cable/DSL modem is also a router. But if the product description says "router", it has router functionality (even though it may also say "access point").

Gateway -- Layer 4~7 network device or server -- sends packets to each machine based on the MAC address, or protocol also can translate other protocols.