Subnetting...WTF

[BustinJustin]

I'm taking a network admin class and my teacher was trying to explain subnetting to me. She says that she has her network set up with a scheme of 172.16.10 (I kinda get that) but she also says that she can have upwards of 65,000 devices on her network. I do NOT understand that. She told me to look at the binary, so here it is:

172 = 10101100

16 = 00010000

10 = 00001010

That leaves one byte in the IP address open to assign to devices, right? That's my understanding of it or at least my teacher didn't explain it any different. That byte has a range of 0-255. That's 256 by my count. WHERE DO 65,0000 COMPUTERS COME FROM? Please explain this to me.

[SubTract]

so the subnet for her IP range is 255.255.0.0

Its been a while since I've done this but essentially.

the number of hosts is determined by the host bits determined by non full subnet address anything that is 0 are host addresses(or devices you can connect) anything at 255 is solely subnets or more networks. and anything between is a combination of both.

if she had a address scheme of 172.16.10.*/255.0.0.0 meaning that the first octet in binary (11111111)represents the network and the next 3 (00000000.00000000.00000000) are available host addresses. meaning that meaning that you would have 256x256x256 available host addresses or 16,777,216 addresses if you change that subnet to 255.255.0.0 (11111111.11111111.00000000.00000000) you change the 2nd octet from host addresses to network addresses giving you 256x256 available hosts allowing you to have 65,536 host addresses.

For her IP addresses if she was going with 172.16.10.0-255 then ran out at 255 she would then change to 172.16.11.0-255 and so on until you ran out of addresses. As long as they're on the same subnet they'll still comunicate.

I hope this helps.

[dharmadrummer]

This is one of my instructors. I haven't watched the video but I was in his class and he does an excellent job of explaining subnetting.

[Broseephus]

She also didn't really give you enough information. No the 172.16.10.xxx will not translate into 65k devices.

It would have to be like 172.16.0.0/16 for it to work. the way she is saying, with so many devices.

She would give her hosts ip addresses anywhere from 172.16.0.0/16- 172.16.255.255/16

[SubTract]

the 16 represents the amount of bits dedicated to network addresses. so if you hat 172.16.10.xxx/8 your subnet would be 255.0.0.0 or 11111111.00000000.00000000.00000000 and if it was /16 the second block of 8 would also be 1's. its a shortened way when writing what the subnet is.

I just thought I would explain incase you didn't know.

Also don't think you're stuck to solid blocks of 8 you could also have 255.255.255.128 meaning it would be /25 or 255.255.255.192 which would be /26

each reducing the umber of hosts connectable a /25 network would be capable of 128 hosts. a /26 network only capable of 64 hosts, /27 is 32 hosts, /28 is 16 and so on. it works the opposite in reverse. a /24 network would be 256 hosts and a /23 would be 512.

I hope I'm not confusing the situation to much.