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Re: HOWTO: Understand Binary and Subnetting
by Don on Tuesday October 22, @05:12AM
I think there is a flaw in your explanation. I don't think you should deduct 2 from the number of possible subnets. It should be deducted from the number of hosts (network ID and broadcast address) Take for example a subnet of 255.255.192.0 with network 10.101.192.0. You have 2 bits in the third octet for the network ID. Using your rule there should be (2x2-2=2) network ID's (64 and 128). So there should be the following networks: 10.101.64.0 through 10.101.127.254 and 10.101.128.0 through 10.101.191.254 What about 10.101.0.0 through 10.101.63.254 and 10.101.192.0 through 10.101.255.254? What do you think?

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    Correct!!! - Take Note
    by s-eye on Tuesday June 24, @08:59AM
    use 2^n and forget the "-2" for determining the number of subnets.

    For /27, n=3 and number of subnets is 8 (2^3=8). Following the post's example, the network numbers for the subnets would be the following:

    192.168.1.0
    192.168.1.32
    192.168.1.64
    192.168.1.96
    192.168.1.128
    192.168.1.160
    192.168.1.192
    192.168.1.224

    Aside from that tweak, I agree with everyone else here - The post is a consice, straightforward intro to real subnetting. Nice Job.
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    Re: HOWTO: Understand Binary and Subnetting
    by Jason on Sunday November 20, @08:21AM
    I agree that it's strange to eliminate the first and last subnet range. The simple answer to your statement is that it's the rule dictated by a lot of router hardware. However, these days those addresses can be used on some router gear. For example Cisco refers to this feature as ip subnet zero on their routers and in recent Cisco IOS versions it is now turned on by default.

    I hope this helps clarify.
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