Subnetting failed

I am reading the Network Fundamentals (CCNA Exploration Companion Guide) from Cisco Press and am on chapter 6 which deals with addressing IPv4 networks. The book has an example on how to subnet the network 192.168.1.0/25 into two subnets with a network mask of 255.255.255.128.

When I use the online subnet calculator the book mentions, it says subnetting failed.

The site I used is VLSM CIDR Subnet Calculator

The message I got and need help interpreting is below. Why does it say that I am using 200% of available major network address space? Is that the error or is it something else?

https://picasaweb.google.com/lh/photo/YNswLYfHi36oxctnRhWaVw?feat=directlink

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Comments

Zartanasaurus

Change the major network to /24. I don't have the book, but I have to assume they mean they want you to subnet 192.168.1.0/24 into two /25 subnets.

JamesFigueroa

Not sure...your subnet is correct for the needs as far as i can tell. I wouldnt worry too much about it. For me you got subnet passed ;p

MosGuy

On the subnet link page:

Major network: 192.168.1.0 /24
Subnet: A & B, space = 126
Number of subnets: 2 , <change> button

"Subnetting Successful" message

JJBladester

Back to the original question:

Given an address block of 192.168.1.0/24, you will create two subnets. You borrow 1 bit from the host portion by using a subnet mask of 255.255.255.128, instead of the original 255.255.255.0.

Thanks guys!