How to determine the valid host range an IP belongs to

How do you determine the valid host range as asked in the below question?

What valid host range is the IP address 172.25.102.41/22 a part of?
Answer: 172.25.100.1 through to 172.25.103.254

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binaryhat

Have you read up on subnetting?

Perhaps if you give us how you went about solving the ? and where you got stuck we help you out.

CertGrabber

Well, the first thing I would ask you is what Class of address does 172 fall under? This is vital. (This would be a Class B address because their range is 128-191) Therefore, be definition, the network mask is 255.255.0.0, or /16...

Now, with a given IP and mask of 172.25.102.41 /22 you can see that they are using 6 bits for subnetting. (/16 default, and now using /22). This is a mask of 255.255.252.0... So there will be 2 bits in the 3rd octet for hosts, as well as the whole 4th octet for hosts. You can calculate the block size by doing 256-252=4. SO, every 4 addresses in the 3rd octet will be a separate subnet. Note that there are 10 host bits, so this gives us (2^10)-2 possible host addresses per subnet.

Now that we got that... let's look at the 3rd octet to find what subnet this address is in.. The value here is 102 and we know every 4 numbers will be a new subnet. So the subnets are 0, 4, 8, 12, 16......100, 104, 108, etc. So, as you can see 172.25.100.0 is the subnet. Now, we know the next subnet will be 172.25.104.0. Knowing this, we just go 1 address under this to get the last address in the 172.25.100.0 network. This will be 172.25.103.254! Class B addresses can be tricky because you have to fill up the last octet before the 3rd octet's number is incremented again.. Hope this helps!!

Monkerz

Click Here --> http://www.techexams.net/forums/ccna-ccent/38772-subnetting-made-easy.html

ccnaomkar

172.25.102.41/22

default class b

172.25.0.0

/22=block of 4

172.25.0.0
172.25.4.0
172.25.---

172.25.100.0-172.25.103.255

so
172.25.100.0-network id
172.25.103.255-broadcast id

ip between is host range
172.25.100.1-172.25.103.254

ccnaomkar

https://learningnetwork.cisco.com/servlet/JiveServlet/previewBody/6014-102-1-19236/Subnetting%20Examples.pdf