Tag: Subnet

Frequently (Un)Asked Questions – Pt. 3

Frequently (Un)Asked Questions – Pt. 3

Previously on FUAQ, I spoke about how IP and MAC addresses are used to send data. On this installment, I will cover subnet masks, private address spaces, and network address translation.

First, let’s pick up where we left off with FUAQ Pt. 2: my computer talking to http://www.google.com.

Recap: My computer (72.240.254.176) wants to send something to http://www.google.com (172.217.4.132). My computer will make a letter to 172.217.4.132 and send it to the post office (router). To send something to the router, my computer (F4:5C:89:XX:XX:XX) will use the local address of the router (08:EA:44:XX:XX:XX). So my computer puts the letter to google in an envelope, writes google’s address on it. Then puts that envelope in a box and addresses the box to my router.

A big issue here is that my computer is using one address, and Google is using another. Why is that an issue? There are only 4 billion addresses available in IPv4! There are more than 4 billion devices in the world, though, so how do we handle this? Network Address Translation (NAT) allows multiple computers to use many private network addresses through one public network address.

Example: A grandmother wants to send a letter to her two grandkids that both live in the same house. When she addresses the letters, they are both sent to the same street address, same town, same state. But thanks to their mother’s intelligence, each letter makes it to the right person.

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