Cannot figure out how many sub & hosts for 10.0.0.0/20

SurferdudeHBSurferdudeHB Posts: 199Member ■■■□□□□□□□
@#$@!! Ok I'm a little frustrated here lol..with this subnetting question.

How many subnets and host can you get out of 10.0.0.0/20 ?

I'm using the 2^N and (2^N)-2 formula.

2^N, N being the # of bits turned on, hence,
IIII IIII.IIII IIII.IIII 0000.0000 0000
so that would be 4 bits?

Comments

  • miller811miller811 Posts: 897Member
    I don't claim to be an expert, but I sure would like to become one someday.

    Quest for 11K pages read in 2011
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  • dynamikdynamik Posts: 12,314Banned ■■■■■■■■□□
    Class A is /8 by default, so you would have 12 bits, not 4.
  • georgemcgeorgemc Posts: 429Member
    4096 subnets with 4094 usable hosts in each subnet.

    What is the default mask for the network?

    /8 or 255.0.0.0 or 11111111.0000000.0000000.0000000

    What is the subnetted mask?

    /20 or 255.255.240.0 or 11111111. 11111111.11110000.00000000

    Looking at the above mask, we borrowed 12 bits for subnetting and have 12 bits left over for hosts.

    Now apply your formulas, 2^12 = 4096, (2^12)-2 = 4094



    @#$@!! Ok I'm a little frustrated here lol..with this subnetting question.

    How many subnets and host can you get out of 10.0.0.0/20 ?

    I'm using the 2^N and (2^N)-2 formula.

    2^N, N being the # of bits turned on, hence,
    IIII IIII.IIII IIII.IIII 0000.0000 0000
    so that would be 4 bits?
    WGU BS: Business - Information Technology Management
    Start Date: 01 October 2012
    QFT1,PFIT in progress.
    TRANSFERRED/COMPLETED: AGC1,BBC1,LAE1,QBT1,LUT1,QLC1,QMC1,QLT1,IWC1,INC1,INT1,BVC1,CLC1,MGC1, CWV1 BNC1, LIT1,LWC1,QAT1,WFV1,EST1,EGC1,EGT1,IWT1,MKC1,MKT1,RWT1,FNT1,FNC1, BDC1,TPV1 REQUIRED:
  • KaminskyKaminsky Posts: 1,235Member
    SurferDude .... this is where you kick yourself and slap your forehead ..... and welcome to the club :)
    Kam.
  • I wrote a white paper on IP addressing I think it makes it pretty easy. I use it on my students at ITT Tech and they get it pretty fast. It may help on some of it. I am currently doing one on VLSM that may be more applicable. I have it on my linkedin site just go in and download it

    Good luck
    Bill

    http://www.linkedin.com/in/firemarshalbill

    icon_study.gif
    Go EVERTON

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  • tech-airmantech-airman Posts: 953Member
    @#$@!! Ok I'm a little frustrated here lol..with this subnetting question.

    How many subnets and host can you get out of 10.0.0.0/20 ?

    I'm using the 2^N and (2^N)-2 formula.

    2^N, N being the # of bits turned on, hence,
    IIII IIII.IIII IIII.IIII 0000.0000 0000
    so that would be 4 bits?

    SurferdudeHB,

    What class is that network address?
  • SurferdudeHBSurferdudeHB Posts: 199Member ■■■□□□□□□□
    SurferdudeHB,

    What class is that network address?

    Class A
  • SurferdudeHBSurferdudeHB Posts: 199Member ■■■□□□□□□□
    Kaminsky wrote: »
    SurferDude .... this is where you kick yourself and slap your forehead ..... and welcome to the club :)

    Thanks I'm doing this daily lol..
  • tech-airmantech-airman Posts: 953Member
    Class A

    SurferdudeHB,

    What is the default mask for a Class A network address?
  • billscott92787billscott92787 Posts: 933Member
    Subnetting Quiz #1

    Subnetting Quiz #2 (CIDR)


    These are pretty helpful to help you practice and really get things down. You can also check out subnettingquestions.com - Free Subnetting Questions and Answers Randomly Generated Online, it is pretty good as well. Good luck and may the force be with you! :)
  • SurferdudeHBSurferdudeHB Posts: 199Member ■■■□□□□□□□
    surferdudehb,

    what is the default mask for a class a network address?

    255.0.0.0
  • SurferdudeHBSurferdudeHB Posts: 199Member ■■■□□□□□□□
    Subnetting Quiz #1

    Subnetting Quiz #2 (CIDR)


    These are pretty helpful to help you practice and really get things down. You can also check out subnettingquestions.com - Free Subnetting Questions and Answers Randomly Generated Online, it is pretty good as well. Good luck and may the force be with you! :)

    Thx Bill!
  • tech-airmantech-airman Posts: 953Member
    255.0.0.0

    What is the difference in bits from 255.0.0.0 to /20?
  • Mark KnutsonMark Knutson Posts: 73Member ■■□□□□□□□□
    Interesting exercise for me to see if I could do it in my head just from the title of the post.

    2^12 subnets, 2^4 -2 hosts.

    PS. All the materials I have seen indicate not subtracting 2 from the number of subnets unless the question gives some sort of hint that the zero subnet is not allowed or some such.
  • Tech I think you are asking what the mask represented by the /20 is versus 255.0.0.0

    If that is it the /20 would mean the first 20 bits of the mask are 1's which would come out as

    255.255.240.0 as the mask icon_exclaim.gif

    The 255.0.0.0 would be a /8
    Go EVERTON

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  • SurferdudeHBSurferdudeHB Posts: 199Member ■■■□□□□□□□
    What is the difference in bits from 255.0.0.0 to /20?

    255.0.0.0 = 1111 1111.0000 0000.0000 0000.0000 0000

    /20 = 1111 1111.1111 1111.1111 0000.0000 0000

    so the difference in bits is 12
  • tech-airmantech-airman Posts: 953Member
    255.0.0.0 = 1111 1111.0000 0000.0000 0000.0000 0000

    /20 = 1111 1111.1111 1111.1111 0000.0000 0000

    so the difference in bits is 12

    SurferdudeHB,

    Including subnet zero, how many subnets can you have with 12 bits?
  • SurferdudeHBSurferdudeHB Posts: 199Member ■■■□□□□□□□
    SurferdudeHB,

    Including subnet zero, how many subnets can you have with 12 bits?

    That would be 2^N N being the number of turned on bits. So 4096 # of subnets.
  • billscott92787billscott92787 Posts: 933Member
    Your right

    2^12 = 4096 subnets. Which leaves 12 host bits 2^12 - 2 = 4094 (since the network and broadcast addresses are reserved.)


    Just remember if IP subnet-zero is in use, you can use the reserved subnets (subnet zero)

    2^n



    If there is NO IP SUBNET-ZERO



    You would use 2^n-2
  • tech-airmantech-airman Posts: 953Member
    That would be 2^N N being the number of turned on bits. So 4096 # of subnets.

    Since the subnet mask is /20, how many bits are left in the IP address for hosts?
  • SurferdudeHBSurferdudeHB Posts: 199Member ■■■□□□□□□□
    Since the subnet mask is /20, how many bits are left in the IP address for hosts?

    12 bits
  • tech-airmantech-airman Posts: 953Member
    12 bits

    SurferdudeHB,

    How many hosts can you have using 12 bits?
  • AndysSumyAndysSumy Posts: 2Member ■□□□□□□□□□
    we have 12 bits for networks and 12 bits for hosts
    12^2=4096 networks
    12^2-2=4094 hosts
    p.s
    ip subnet-zero is default for cisco router
  • SurferdudeHBSurferdudeHB Posts: 199Member ■■■□□□□□□□
  • tech-airmantech-airman Posts: 953Member
    4094 hosts.

    SurferdudeHB,

    Looks like NOW you CAN figure out how many sub & hosts for 10.0.0.0/20. :)
  • SurferdudeHBSurferdudeHB Posts: 199Member ■■■□□□□□□□
    SurferdudeHB,

    Looks like NOW you CAN figure out how many sub & hosts for 10.0.0.0/20. :)


    Thank you Tech-airman!
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