[MLB-WIRELESS] Waterproof Boxes & IP Allocation

[Chris Samuel]

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On Tuesday 29 Apr 2003 10:57 am, Dan Flett wrote:

> What is an IP Block?  Is it a range of IP addresses that the node can use? 

Exactly correct, well guessed.

> What is the /28 part of the address?

IPv4 (standard Internet IP addresses, rather than new, funky, IPv6 ones) use 
32 bit values.  The /28 means that the first 28 bits of the address are used 
for the "network address" of the block, leaving the bottom 4 bits for the 
"host address".  To work out the maximum value of a binary value you take the 
number of bits to the power of two (because binary has just two values per 
bit), so you get 4^2 addresses = 16.

Now, you loose two of those automatically because one becomes the network 
address (the lowest possible value) and one becomes the broadcast address 
(the highest possible value).  Never put a host as one of those!

So, as an example from one of the ones you quoted:

10.10.144.128/28

The network address is 10.10.144.128.
The broadcast address is 10.10.144.143
Hosts can be in the range 10.10.144.129 -> 10.10.144.142

There's a neat utility called "ipcalc" that comes with some Linux 
distributions that can work these sort of things out for you, e.g. :

$ ipcalc -n 10.10.144.128/28
NETWORK=10.10.144.128

$ ipcalc -b 10.10.144.128/28
BROADCAST=10.10.144.143

The "$ " is just the prompt of the command line.

Oh, I mentioned IPv6 earlier, that uses 128 bits of addressing, so you get 4 
times as much address space, billions & billions of possibilities (where's 
Carl Sagan when you need him?).

> And how does one get a block allocated to them?

Er, pass on that one. :-)

- -- 
 Chris Samuel  :  http://csamuel.org/  :  Melbourne, VIC

 Need someone with 10 years of Linux, Unix, Networking
   & IT Security skills in Melbourne, VIC ? Email me.
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