[TriLUG] OT: IP subnetting question

[Brian Henning]

Hi Folks:

I just worked out a contract with a service provider for internet service.
I noticed that they offered the following static IP packages:

/30, 1 useable address
/29, 5 useable addresses
/28, 13 useable addresses

My question is: For each of those, that leaves three "unuseable" addresses.
What are they for?  I made some guesses:

- broadcast address (all ones)
- ?????????         (all zeros) (does this have a name?)
- Modem's own address

Thanks for the input!
~Brian

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          Brian Henning, Software Engineer

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