Subject: Re: netmask/broadcast questions
To: SamMaEl , Robert Nestor <rnestor@metronet.com>
From: Henry B. Hotz <hotz@jpl.nasa.gov>
List: port-mac68k
Date: 12/31/1997 11:22:47
At 4:15 PM -0800 12/30/97, SamMaEl wrote:
>	My new setup is:
>
>IPs 192.168.1.*               # with 1-4 being used
>netmask 255.255.255.0         # which for a class C subnet SHOULD be right?
>broadcast 255.255.255.192     # ?? no clue on this one...
>
>	So, for the above setup, 1) is the netmask I set correct, and 2)
>what the &*(^ would my broadcast be? ;-) I'm going to re-ifconfig here in

First ifconfig should "do the right thing" for the broadcast address if you
give it the right netmask.  The only reason you should worry about it is if
you have some old (BSD 4.2 or SunOS 4.x ?) machines on the network which
use zero bits for the broadcast address instead of one bits.

To answer the question specifically, for the IP and netmask you specify the
broadcast address would be 192.168.1.255

While the class A/B/C/D distinction restricts the netmask it does not
determine it.  192... is a class C, but it could have a netmask of
255.255.255.128 255.255.255.192, 255.255.255.224, 255.255.255.240, etc.
(If you don't see the pattern then convert the last number to binary.)

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