VLSM, Subnetting Question

Hey guys,
so I was watching the videos and Keith gave this example:
Using this network:
create a subnetwork for 220 hosts, and another one for 45 hosts.
I know that going to /24 we can support 254 hosts. So Keith listed the network the following way: and what is the max range here? He didn't provide the sample. And he moved on to the next network for 45 hosts this way: to

My question is, why is it x.x.1.0??? How does this work? Can someone please break it down for me.
Also, what's the max range for this network for 254 hosts with a subnet mask of /24? Is it I'm lost here.

Please help!!



  • MartinlMartinl ✭✭✭
    edited December 8

    Find other video(s) about VLSM that explains it if one u watching now does not work for you. also, you must know inside/out regular subnetting before going into VLSM.

    1. Main thing about is VLSM is that it uses block structure of 2,4,8,16,32,64,128,254,etc.
    2. Start with the largest number of hosts requirement.
    3. Find Magic number table (also magic number subnetting way) to use in vlsm.
    4. start at 0

    so, 2 networks, one with 220 hosts, and one for 45 hosts. - is the range u can work with for /22.

    220 falls into group 254, 8 bit used up, aka /24 is used up for 1st network with 220 hosts. Range - 0.254; B-caast 0.255

    next up is 45 falls into 64 block, /26 which gives u 62 hosts. starting where u ended up, range is to next up is, then would be x.x.1.128, then x.x.1.192. then , if u continue with 63 hosts (block of 64), network x.x 2.0, xx.2.64, x.x2.128, xx.2.192. finally, x.x.3.0 thru 3.255 is your last range since u have /22 to begin in first place.

    if u would need 2 networks for 220 hosts, then for 45 hosts, answer would be:
    next range available is

    see my magic table below

  • Hey Martini,
    Thanks for clearing this up. I've actually been doing a lot of subnetting practice since I made this post and now I got it down. Your answer made it even clearer and I appreciate that. Your breakdown made things even simpler, I feel more confident doing these problems now.

    Thank you.

  • MartinlMartinl ✭✭✭

    no problem

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