Subnetting question

What is the first valid host on the subnetwork that the node 172.27.103.132 255.255.255.128 belongs to?

plz help me by givin me a simple explanaton for this question...
thanku

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rob42

vtiniall wrote: »

Thanks for taking the time to write out the solution. It does help alot

You're welcome. It's not easy to get your head around, but once you do, it kind of sticks.

Feel free to ask about anything that you're unsure of.

Edit to add...

There are quite a few threads on here about the subject, I'd suggest you read them and find a system that chimes with your own way of thinking.

vtiniall

Just one last question. How would you chart work for this question

[FONT=&quot]What is the last valid host on the subnetwork 172.27.154.0 255.255.254.0?[/FONT]

rob42

vtiniall wrote: »

Just one last question. How would you chart work for this question [FONT=&amp]What is the last valid host on the subnetwork 172.27.154.0 255.255.254.0?[/FONT]

In this example, the 3rd Octet is where the Network and the Hosts split (as dictated by the Mask), so it's the 3rd Octet that we're interested in. Look at the Mask column for 254 and sub-rows 3 (because we're interested in the 3rd Octet) for the CIDR and Host Bits, you'll see the the CIDR is /23 (meaning 23 Network bits) Host bits = 9, and the Block Size is 2. The Block Size is value by which the Subnet Address changes, starting at zero and incrementing by two (the Block Size) in this example, for each Subnet...

1st Subnet = 172.27.0.0
2nd Subnet = 172.27.2.0
3rd Subnet = 172.27.4.0
4th Subnet = 172.27.6.0
...etc...
77th Subnet = 172.27.152.0
78th Subnet = 172.27.154.0
79th Subnet = 172.27.156.0

You can quickly arrive at the 78th Subnet with a little math: Octet Value / Block Size, plus one (154/2 = 77 + 1 = 7

.

So, the 78th Subnet is 172.27.154.0 and the Broadcast is 172.27.155.255, which is one IP Address down from the 79th Subnet (172.27.156.0).

The valid Host IPs are between the Subnet IP and the Broadcast IP -- 172.27.154.1 -> 172.27.155.254

My **** Sheet simply gives you the important information you need (block size, CIDR {which is also the number of Network bits}, Mask and number of Host bits) in order to quickly see where the boundary is between the Network IP and the Host IPs, for any given IP Address. You still need to understand how that information is applied.

Here's one for you to do.

IP = 179.20.55.28 /22

Which Subnet?
What is the Subnet IP?
What are the first and last Valid Host IPs
What is the Broadcast IP?
What is the Subnet Mask?