Another subnetting calculation question...Scott?

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Okay, I've learned how to take an IP address and mask and determine
the network address.  I know 2 methods:  The "Magic Number" easy
method from Odom's videos, and the binary AND method which I use to
check my answer.

So then we move on to determining the broadcast address, as well as
host range.  We learned yet another "Magic Number" method:  Magic
Number plus relevant octet of network address, minus 1.

Example:

Mask:       255.255.224.0
IP:           128.200.100.100
Network: 128.200.96.0  (Easy:  256 - 224 = 32.  96 is the multiple of
32 without going over 100, so it's 96).  Binary ANDing 224 and 100 is
just as easy.

1st usable host IP:  128.200.96.1.  Again, simple.  Network address
+1.

Now:  We're taught that to find the broadcast address, take 96, add
the magic number (32) = 128, subtract 1, and we get 127.

Simple enough to memorize, but doesn't satisfy me.
How do we get there the "hard" way, without using a formula?

I'm assuming there's a binary method to get from the network or IP
address to the broadcast address?

Re: Another subnetting calculation question...Scott?


The Binary Method for getting the Broadcast Address is to set all host
bits int the IP/network Address to 1.

Example:
Network 192.168.1.160/29 i.e 255.255.255.248

Binary:  11000000.10101000.00000001.10100000
Netmask: 11111111.11111111.11111111.11111000
so setting the last 3 bits in the binary represantation of your IP
address/Network address leaves you with:

Binary:  11000000.10101000.00000001.10100111
which is the correct broadcast address: 192.168.1.167

Mitch@_._ schrieb:
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Re: Another subnetting calculation question...Scott?



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Thanks!  That's exactly what I was looking for.

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