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Cedar Rapids, Iowa | Short answer:
A subnet mask tells the computer how big the local network is. This would be clearer if you saw the IP addresses in binary form instead of dotted decimal. A common subnet mask is 255.255.255.0, also known as "/24" or a "Class C" subnet. In binary form, there are 24 1s, and 8 0s, as the IP address is 32 bits long. If your computer needs to send data to any IP that starts with the same 24 bits that your computer has, it knows the other device is local. Otherwise, that device isn't local and the packet needs to be forwarded to the default gateway. For example, if your computer has an IP address of 192.168.1.2 and a subnet mask of 255.255.255.0, then it knows the any destination address of 192.168.1._ is local, and everything else needs to go to the default gateway.
A default gateway is where your computer sends all packets that it can't get to locally. Think of it like your local post office. If you wrote a letter to anyone in your house, you can just hand it to them. If you write a letter to anyone else, you put it in your mailbox, and the post office takes care of getting it to the destination. It doesn't matter if the destination is your next door neighbor, or someone on the other side of the globe. In fact, there is a FROM and TO address on every single packet of data that moves on the Internet, just like the post office.
Long answer: google for "what is a subnet mask" and "what is a default gateway" and start reading. | |
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teach me about ip address's, default gateways, and subnet masks
