range of ip addresses

Hey!!

I came across this question.

What valid host range is the IP address 172.19.13.52/23 a part of?

The answer is 172.19.12.1 through to 172.19.13.254

I only figured out the first address but I couldn't figure out the second
address. Could someone explain the range to me?

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Comments

Highspade

Next subnet is 172.19.14.0 with a range of 172.19.14.1 - 172.19.15.254

luke_bibby

Figure out the dotted decimal subnet mask for a /23 network:
/23 = 255.255.254.0

The 'interesting' octet is the 3rd one in the subnet mask, as it is the only one which is neither a 0 or a 255.

Calculate the magic number (which is given by 256 - the subnet mask's interesting octet):
m = 256 - 254 = 2

From the magic number, you now know that the subnets jump in 2's, so:
First subnet = 172.19.0.0 - 172.19.1.255
Second subnet = 172.19.2.0 - 172.19.3.255
....
Seventh subnet = 172.19.12.0 - 172.19.13.255
Eighth subnet = 172.19.14.0 - 172.19.15.255

The first and last IP address in a subnet is unusable as the first IP is the subnet number and the last IP is the broadcast number. Therefore, to answer your question, the valid host range for the subnet mask which the IP address 172.19.13.52 belongs to is 172.19.12.1 - 172.19.13.254

jamesleecoleman

Thanks for the explaination luke bibby. Would this also work for

What valid host range is the IP address 172.30.83.160 255.255.248.0 a part of?

Answer: 172.30.80.1 through to 172.30.87.254

as well??? I'm getting the magic number of '8' but I would go over the range.

M4verick

jamesleecoleman wrote: »

Thanks for the explaination luke bibby. Would this also work for

What valid host range is the IP address 172.30.83.160 255.255.248.0 a part of?

Answer: 172.30.80.1 through to 172.30.87.254

as well??? I'm getting the magic number of '8' but I would go over the range.

8 is correct. Remember to start at 0, and include that first subnet when counting.
Like, 172.30.80.1/21 doesn't end at 172.30.88.254.
You'd count 80, 81, 82, 83, 84, 85, 86, 87. You're done there.

172.30.0.1 - 172.30.7.254
172.30.8.1 - 172.30.15.254
...
172.30.72.1 - 172.30.79.254
172.30.80.1 - 172.30.87.254

captobvious

Subnetting Made Easy

jamesleecoleman

Thanks M4verick and captobvious!! I think I understand it. I'll post back if I have any more trouble.