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Cannot figure out how many sub & hosts for 10.0.0.0/20
SurferdudeHB
Member Posts: 199 ■■■□□□□□□□
in CCNA & CCENT
@#$@!! Ok I'm a little frustrated here lol..with this subnetting question.
How many subnets and host can you get out of 10.0.0.0/20 ?
I'm using the 2^N and (2^N)-2 formula.
2^N, N being the # of bits turned on, hence,
IIII IIII.IIII IIII.IIII 0000.0000 0000
so that would be 4 bits?
How many subnets and host can you get out of 10.0.0.0/20 ?
I'm using the 2^N and (2^N)-2 formula.
2^N, N being the # of bits turned on, hence,
IIII IIII.IIII IIII.IIII 0000.0000 0000
so that would be 4 bits?
Comments
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Optionsmiller811 Member Posts: 897I don't claim to be an expert, but I sure would like to become one someday.
Quest for 11K pages read in 2011
Page Count total to date - 1283 -
Optionsdynamik Banned Posts: 12,312 ■■■■■■■■■□Class A is /8 by default, so you would have 12 bits, not 4.
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Optionsgeorgemc Member Posts: 4294096 subnets with 4094 usable hosts in each subnet.
What is the default mask for the network?
/8 or 255.0.0.0 or 11111111.0000000.0000000.0000000
What is the subnetted mask?
/20 or 255.255.240.0 or 11111111. 11111111.11110000.00000000
Looking at the above mask, we borrowed 12 bits for subnetting and have 12 bits left over for hosts.
Now apply your formulas, 2^12 = 4096, (2^12)-2 = 4094SurferdudeHB wrote: »@#$@!! 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: -
OptionsKaminsky Member Posts: 1,235SurferDude .... this is where you kick yourself and slap your forehead ..... and welcome to the clubKam.
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OptionsFiremarshalbill.com Member Posts: 128I 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
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Optionstech-airman Member Posts: 953SurferdudeHB wrote: »@#$@!! 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? -
OptionsSurferdudeHB Member Posts: 199 ■■■□□□□□□□tech-airman wrote: »SurferdudeHB,
What class is that network address?
Class A -
OptionsSurferdudeHB Member Posts: 199 ■■■□□□□□□□SurferDude .... this is where you kick yourself and slap your forehead ..... and welcome to the club
Thanks I'm doing this daily lol.. -
Optionsbillscott92787 Member Posts: 933Subnetting 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! -
OptionsSurferdudeHB Member Posts: 199 ■■■□□□□□□□tech-airman wrote: »surferdudehb,
what is the default mask for a class a network address?
255.0.0.0 -
OptionsSurferdudeHB Member Posts: 199 ■■■□□□□□□□billscott92787 wrote: »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! -
Optionstech-airman Member Posts: 953SurferdudeHB wrote: »255.0.0.0
What is the difference in bits from 255.0.0.0 to /20? -
OptionsMark Knutson Member Posts: 73 ■■□□□□□□□□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. -
OptionsFiremarshalbill.com Member Posts: 128Tech 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
The 255.0.0.0 would be a /8 -
OptionsSurferdudeHB Member Posts: 199 ■■■□□□□□□□tech-airman wrote: »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 -
Optionstech-airman Member Posts: 953SurferdudeHB wrote: »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? -
OptionsSurferdudeHB Member Posts: 199 ■■■□□□□□□□tech-airman wrote: »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. -
Optionsbillscott92787 Member Posts: 933Your 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 -
Optionstech-airman Member Posts: 953SurferdudeHB wrote: »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? -
OptionsSurferdudeHB Member Posts: 199 ■■■□□□□□□□tech-airman wrote: »Since the subnet mask is /20, how many bits are left in the IP address for hosts?
12 bits -
OptionsAndysSumy Member Posts: 2 ■□□□□□□□□□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 -
Optionstech-airman Member Posts: 953SurferdudeHB wrote: »4094 hosts.
SurferdudeHB,
Looks like NOW you CAN figure out how many sub & hosts for 10.0.0.0/20. -
OptionsSurferdudeHB Member Posts: 199 ■■■□□□□□□□tech-airman wrote: »SurferdudeHB,
Looks like NOW you CAN figure out how many sub & hosts for 10.0.0.0/20.
Thank you Tech-airman!