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

SurferdudeHB
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**198**Member ■■□□□□□□□□
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?

0

## Comments

897MemberQuest for 11K pages read in 2011

Page Count total to date - 1283

12,314Banned429MemberWhat 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.

11111111.11110000.00000000Looking 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

WGU BS: Business - Information Technology ManagementStart 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:

1,235Member128MemberGood luck

Bill

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

648MemberCCNA:S

Don't be a dumper!

953MemberSurferdudeHB,

What class is that network address?

198Member ■■□□□□□□□□Class A

198Member ■■□□□□□□□□Thanks I'm doing this daily lol..

953MemberSurferdudeHB,

What is the default mask for a Class A network address?

933MemberSubnetting 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!

198Member ■■□□□□□□□□255.0.0.0

198Member ■■□□□□□□□□Thx Bill!

953MemberWhat is the difference in bits from 255.0.0.0 to /20?

73Member ■■□□□□□□□□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.

128MemberIf 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

198Member ■■□□□□□□□□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

953MemberSurferdudeHB,

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

198Member ■■□□□□□□□□That would be 2^N N being the number of turned on bits. So 4096 # of subnets.

933Member2^12 = 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

953MemberSince the subnet mask is /20, how many bits are left in the IP address for hosts?

198Member ■■□□□□□□□□12 bits

953MemberSurferdudeHB,

How many hosts can you have using 12 bits?

2Member ■□□□□□□□□□12^2=4096 networks

12^2-2=4094 hosts

p.s

ip subnet-zero is default for cisco router

198Member ■■□□□□□□□□953MemberSurferdudeHB,

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

198Member ■■□□□□□□□□Thank you Tech-airman!