Another Example: Let’s say our address is 10.10.1.99/23 In Binary that becomes 00001010.00001010.00000001.01100011 The network portion is determined by the ones in the subnet mask.So /23 means the network portion is the first 23 bits as is, with the remainder of the bits set to 0 00001010.00001010.00000000.00000000 So 10.10.0.0 it the network address Broadcast address: set those last bits to 1’s instead of 0's (everything after the 23 bits from subnet mask)00001010.00001010.00000001.11111111 So 10.10. 1.255 is the broadcast address 1st available host address - add one to the network adress00001010.00001010.00000000.00000001 So 10.10.0.1 Last available host address - subtract one from the broadcast address00001010.00001010.00000001.11111110 So 10.10.1.254 Range of host address is therefore 10.10.0.1 - 10.10.1.254
good teacher but there`re something is missing "broadcast "keyword is not accurate teriminology instead it`s called "directed broadcast ip address" because "broadcast "keyword by itself is referring to "limited broadcast ip address" and it`s 255.255.255.255 this format 255.255.255.255 is reserved for "limited bc ip addr"or as you say "broadcast" but into your example "10.10.1.255"is called "directed bc ip addr" but if you are already know the difference between these 2-terminologies then it`s ok to say "broadcast" on "10.10.10.255" HTH
Here the address is "10.10.1.99/23". How will I find host, network and broadcast address if I'm not provided with this "/23" mask in the question?? Do I add this subnet mask extension on my own or what? What difference will it make in subnetting if we are provided with an IP address with no subnetting mask extension and we are supposed to determine the network, broadcast and host address? For example last week my teacher gave a subnetting question to find host, network and broadcast address with an IP address "172.16.0.0" with no extension of subnet mask. However in this question, you have clearly used this "/23" Is that any different from when the subnet mask is already given??? Please explain this to me!!
Kim, I'm honestly amazed by you. Every time I don't understand something in particular, be it something about BGP, GRE..anything it is, almost always I'm missing the part that makes me go "That's it! I get it!" - I then search through numbers of books, videos, but I rarely find what I'm looking for. Then I find you!! And you always explain exactly what I've been missing and always deliver it in a way that makes me confident that I do understand a particular subject on a level that I can move on to more advanced stuff. Kim I wish you were making more videos, or had a page or something where we can ping with you more often. Thank you so much for your videos and I'd be so happy if you'd make more!!! High five!
You have been away for too long. Please come back. You explained something so complicated in such a simple way. I figured out a network+ question after watching your video.
Just spent an hour with my friend trying to reverse engineer this subnetting stuff. And just wanted to say this video is what made it all click. Thanks!
There is like hundreds of videos of this on youtube, one worse than the other. This one I borrow and show on my network 101 training classes. Short and not full of "ops". Thank you! I've also noticed some disturbing comments here. Thank you Kim for contributing to a more equal society. We need more women in the business.
I stumbled across this video while working on a subnet calculator project. of all the subnetting lessons on youtube, this was the most helpful. thank you.
This is very helpful as to understand where subnetting nr's come from but use the Magic nr it's easier : 1. CIDR = /26 - that means 8 bits (11111111.) + 8 bits (11111111) + 8 bits (11111111) + 2 bits (11000000) or 8+8+8+2 = 26 So in binary = 11111111.11111111.11111111.11000000 or 255.255.255.192 2. Now to get the magic nr : 256 - 1st subnet in this case 192 (The subnet that you are actually using that won't go unchanged so the one that is not 255) For example if your subnet was 255.255.128.0 you would use the 3rd octet (128) not the last. So 256 - 192 = 64 3. Now 64 is your magic nr also the increment of the network (0, 64, 128, 192, 256) 4 Network = 0 as 34 falls in between the 0 - 64 increment and 0 is the 1st value of this subnet 5.Broadcast = 63 ( last value in subnet - 1) this is because your subnets go from 0-63 and then 64 - 127 and then 128 - 191 etc. 6.Hosts = 1-62 (can't use network address or broadcast address for hosts)
Thank god you do the ones with cidr blocks. So many tutorials that do some really basic subnetting and they all suck because it's so basic... they use the easiest formulas like 255.255.255.0 and in life we know we don't get it that easy. Thank goodness for this video!
Understanding the C language and distinctions between how numbers are represented including how binary is counted and "moves" is important to understand how stuff like this works - why it works the way that it does - and how subnetting works and why its important. Using a subnet is a means to find the NET_ID and HOST_ID of the IPv4 address format represented in decimal against 3 different "standard classes" of addresses. When you see the decimal number "255" that is translated into 11111111 in binary in which the logical AND operator is applied in C to determine where to look for what. She is demonstrating something called variable length subnetting which is a step up that offers flexibility that isn't restricted by byte boundaries, aka the "/8 /16 /24" you see when determining the NET_ID and HOST_ID (IPv4 addresses are 4 bytes or "/32"). In C the char data type's (or byte's) maximum value is 256, which translates to "255" in decimal because we start counting at '0' not '1'. It's always bugged me trying to make sense of what other people said when I was learning about stuff like this because there are multiple layers of abstractions and techniques being discussed. In the case of addressing its bit manipulation and shifting back and forth from decimal to binary. blah blah blah, aight Im out -
Outstanding video tutorial! I’ve viewed many of these over the years and this one may be the best I’ve seen at presenting information clearly in a short amount of time.
For those confused about the Broadcast ID the number you get from adding the 1's is added to whatever number the network ID is. Took me forever to figure that out lol
Ahhh now I see. Thanks for the explanation because my professor's notes just weren't doing any justice. Classmates weren't much help either, so thanks a bunch!
Thank you so much for the explanation! This is such an easy method for figuring out Net ID and Broadcast ID! I just couldn't wrap my head around it before watching this video. Thanks again!
Im about to take my CCENT and I can't thank you enough for this perfect explanation of subnetting, thank you so much Cisco Kim I definitely have to show you to others!
Your video is old but it SAVED my butt I just could not understand it, but your video helped me understand it. Thank you very much. Hope you are doing great in life.
Two rules and everyone can do it, even my nephew 11 years old calculated it in 2 minutes with these rules: A bitwise AND (X) between the IP and Subnet Mask would give us the network address: A bitwise OR (+) between the network address and the inverted subnet mask would give us the broadcast address:
Q. What are the subnet mask, first available host address of subnet one (NOT subnet zero), and the maximum number of hosts per subnet for the network below? You need to allow for maximum number of hosts. Also, you can use subnet zero and the all-ones subnet. RFC 1878 Network ID: 161.31.0.0 Subnets Required: 45
This is the BEST break down I've ever had. Thank you so much. I have one question. Where did you get the /26 from? Like where does this number come from?
it's called a CIDR it's derived from how many hosts you need so if you need say 100 hosts you'd take 2^7 (128) subtract 7 from 32 and it would get you your CIDR which would also get you your subnet 11111111.11111111.11111111.10000000
The only thing that lost me on this video is the bits based on the subnet class. If based on the class identified which is Class B 128-191 the subnet default would be 255(8).255(8).0.0 which would be a 16 bit octet so how did you get 26? A 24 bit would have the subnet class default of 255(8).255(8).255(8).0, right?
I usually do not comment on videos, but I can't hold myself back from saying; nice job CiscoKim, keep it up, I personally benefit a whole lot from the simplicity and clarity of your explanation. Thanks
please Kim i have a question , can i find mask , subnets and number of hosts if i only have a network id ?? for example " Q. What are the subnet mask, first available host address of subnet one (NOT subnet zero), and the maximum number of hosts per subnet for the network below? You need to allow for maximum number of hosts. Also, you can use subnet zero and the all-ones subnet. RFC 1878 Network ID: 174.180.0.0 Subnets Required: 5 "
