I'll give this one a go. Since you're new to TCP/IP you have to understand that all of the IP Addresses and Subnet Masks are written in Decimal to help us understand them a little better. The computers take the Decimal and translate them into Binary. So
255.255.255.255. to us, looks like 11111111.11111111.11111111.11111111 to a computer
Now knowing this...
10.10.10.34/28 means how many bits are used in the Subnet Mask for the Network Address. The remainder us used as the Host address.
28 bits means that....
11111111.11111111.11111111.11110000
When you translate the above binary number into Dec. You get.... 255.255.255.240 <- this is the subnet mask of 10.10.10.34/28 network
10.34.0.0/16 would translate to a subnet mask of...
255.255.0.0 or
11111111.11111111.00000000.00000000
So to answer your question the /28 is the number of bits used as the network address in a subnet mask.
I hope this answers your question....
david e *end users are just like computers, some you can work with...others just need a simple reBOOTing to fix their problems.*
To break sobak's answer down some more for you so you can figure out how he took the /28 and got 255.255.255.240 you do this. The IP/Subnet mask is broken down into 4 "octets" or 4 groupings of 8 digits. So an IP of 10.10.10.34 has 4 groups of numbers, 3 groups of 10 and 1 group with 34. The mask is doen the same way. Now to figure an IPaddress or subnet mask from Binary you figure each grouping like this.
192.168.1.0 > Binary 11000000.10101000.00000001.00000000
Now the inorder to understand the binary you must understand how it is broken down.
192 = 11000000
there are 8 digits in each octet. 1+1+0+0+0+0+0+0
That have a specific value assigned to it.
Once you understand how to break an IP address down to its binary and back then the other addresses will be easy to do. Subnet mask is the same way.
So when you see an address such as 10.10.10.34/28
You will know how to break the IP address down to binary
00001010.00001010.00001010.00100010
So what about the /28 for subnet mask? Just as stated above the /(number) would be the number of bits in an IP address. a bit is represented by 1. So 28 is
11111111.11111111.11111111.11110000
If it was /16 it would be 16 1's followed by 16 0's (there are 32 bits in an IP address (4 groups of 8)
11111111.11111111.00000000.00000000
Then you would just take that number and apply what I showed above to each section.
Learn subnet.com is a great site. You can also use a sientific calculater that is in accesoris on your pc to convert these numbers to octets and play with the numbers above so you can actually see what they mean. Glen A. Johnson
Microsoft Certified Professional
glen@nellsgiftbox.com
"Everything becomes a little different as soon as it is spoken out loud."
Hermann Hesse (1877-1962); German-born Swiss writer.
And another way to look at it is take the last numeric octect (240) subtract it from (255) (which is the full value of that octet)240-255 which = 15 and subtract 1 and get 14 hosts for that network. Understand? James Collins
Field Service Engineer
A+, MCP
email: butchrecon@skyenet.net
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