So I'm working on the last question under the section "Determine Subnet IDs and Ranges of Host IDs", scenario 10. From another website Mindwerks.com, it's way of teaching you to subnet says to determine the # of bits required to support the total # of subnets, you take the # of subnets needed, and convert it to binary. In scenario 10, they have 3 physical segments, so this in binary is 0000011, or the rightmost 2 bits, the 1 & 2 bit.
Then you take that count of 2 bits, and go from the left to right of the binary chart, and add those bits together, i.e. 128+64=192. This is your subnet mask ID. This has worked for every other question on the learntosubnet.com site, aside from scenario 10. From reading the answer, I can see why they selected the subnet mask, but I don't see how you would determine this without just 'knowing' this is how it works.
Can someone explain this scenario to me a little better? I would expect Cisco would throw something like this example on the CCNA to just confuse me more! I've included the 2 link to the sites I'm reviewing. Thanks in advance, Tony
Scenario 10 says that the required number of physical segments is 5. That is the same as saying that they require 5 subnets. The next line says "Maximum Number of Hosts/Physical Segment" is 25. That tells me that the maximum number of hosts that will be on each subnet is 25 hosts. The smallest subnet size, using these conditions, is 32. That gives me a subnet mask of 255.255.255.224. That subnet mask has 30 usable hosts per subnet, and 6 total subnets (8, if we use ip subnet-zero).
Does that help? They are just using different terminology to describe things. The required number of physical segments is the same as saying that you will need at least X amount of subnets.