When I talked about IP addresses, I mentioned default gateways, but didn't go into any details about them at the time. The default gateway is one of the three basic network interface configuration elements of IP networking along with the IP address and the subnet mask. A default gateway is usually, but not always necessary to have a working IP network configuration. As I stated last time, you might know you need to configure a default gateway, but not why.

The default gateway is a host, identified by its IP address, on the local network to which you send packets when the destination address is not on the local network. The default gateway will then, hopefully, forward the packets toward the destination network. But what does all that mean?

If you've grown up in a world where TCP/IP is the only network protocol then your understanding of the basic network interface configuration elements: IP address, subnet mask, default gateway might be purely functional. You know you need to configure these elements, but you might not understand why.

As the older generation of technologists age out of the profession, some of the technical history gets lost in the shuffle. The reasons behind why we do things is forgotten and we just do those things the way it's always been done. Don't mistake me for a cranky old man yelling at the cloud; this convenience is wonderful as we all get to stand upon the shoulders of giants and see a more distant horizon.

Let's climb back down from the giants' shoulders and look at what an IP address is and a bit about why subnet masks are necessary.