I'm going through subnetting, and w 1

[binarysoul]

I'm going through subnetting, and wanna see if I'm right.

Q1.You have the IP address 142.12.0.0 and you have borrowed 4 bits for subnetting. What is the subnet mask?
A1. 255.255.240.0

Q2. You have been 192.16.17.0 for your network. You need to create 16 subnets. How many bits do you need to borrow from the host portion of this address to create 28 subnets?
A2. 5

Q3.You have been 132.16.0.0 for your network. You need to create 256 subnets. How many bits do you need to borrow? A3. 9

Thanks.

 

[ElijahBaley]

Q1.You have the IP address 142.12.0.0 and you have borrowed 4 bits for subnetting. What is the subnet mask?
A1. 255.255.240.0

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This looks OK to me, check the values of the borrowed host bits:

nnnnnnnn.nnnnnnnn.nnnnnnnn.sssshhhh
1631
2426
8
255.255.255.240

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Q2. You have been 192.16.17.0 for your network. You need to create 16 subnets. How many bits do you need to borrow from the host portion of this address to create 28 subnets?
A2. 5
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Yep 5 borrowed host bits will provide for 32 subnets

2^1=2
2^2=4
2^3=8
2^4=16
2^5=32
2^5=32
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Q3.You have been 132.16.0.0 for your network. You need to create 256 subnets. How many bits do you need to borrow? A3. 9
------------------------------------------------------------
Yep you need 9 borrowed host bits to provide for 256 subnets - (you can not have all subnet bits switched on)

Subnet = 132.16.255.1


2^1=2
2^2=4
2^3=8
2^4=16
2^5=32
2^5=32
2^6=64
2^7=128
2^8=256
2^9=1024


EB

 

[svermill]

I have to disagree somewhat, but it depends on what you're studying with. Is Cisco course literature still pushing that old theory that subnet zero isn't usable? Because use of subnet zero has been the default behavior on Cisco routers for years. And the all-ones subnet has always been valid as far as I know. 16 subnets in the "real world" would only require 4 bits, but if your course material for a particular exam still says otherwise, I guess you're better off to defer to them.