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Subject
- Posted on
October 2, 2008, 3:45 pm

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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