What does the slash mean in an IP address?
In: 53
It’s a CIDR Block.
Basically, an IP address is just a giant series of bits. Something like 192.168.1.1 is actually just 11000000.10100000.00000001.00000001 (dots added for readability).
One important concept with IP addresses is the idea of a network. On a network, everything can technically talk to everything else (although not everything may be listening). From my phone on my network, I can access my computer, my server, my laptop, my streaming stick, and many other devices. They are all on the same network and can talk directly to one another.
However, if I wanted to talk to reddit from my phone, it’s on a different network, so I have to go through my router (often referred to as default gateway) to get there.
My phone knows it’s not on the same network because on top of its IP Address, my phone also has a subnet mask. A typical one would look something like 255.255.240.0, or 11111111.1111111.11110000.00000000 if expanded in binary. My phone knows if something else is on the same network or not if the destination IP address has all the same bits set in the IP address that are also set in the subnet mask.
Now, subnet masks are not the most convenient form to write stuff in all the time, and they are largely (although not necessarily) a direct divide between 1s on the left and 0s on the right, so an alternative notation that is used is the CIDR Block. This is where I might write my network address as “192.168.128.0/24”, where that **/24** represents how many 1’s my subnet mask has.
This is beneficial in a few spots, including making it easier to document, and immediate visibility of how many bits are leftover for actually giving addresses to things.
Latest Answers