Another subnetting calculation question...Scott?

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?

Reply to
Mitch
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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:

Reply to
Inga Mewes

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

Reply to
Mitch

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