Could anyone explain to me what exactly the "Broadcast" IP address is? I have changed networks and there is one machine here running SCO Unix V/386 release 3.2... anyways I changed all the ip values, except for the "Broadcast" one in the "etc/tcp" file and I was wondering what exactly that IP address is and how I figure out what I need to change it to?

Try this link - I noticed most of your questions have to do with this type of subject so I thought it would help.

http://hdallen.home.mindspring.com/subnet.htm

Ok let's see if you can get it by these examples

1) 192.168.20.0 submask 255.255.255.0 (or 192.168.20.0/24)

this is a class C IP :
Network IP is :192.168.20.0
Broadcast IP is:192.168.20.255

These two show the start and stop range of the IPs you can use
in this example you can beging using 192.168.20.1 (not ....20.0)
up to 192.168.20.254(not ....20.255)

OK?


2) 192.168.20.0 submask 255.255.255.128 (or 192.168.20.0/25)

this is the first part of a class C divided IP

Network IP is :192.168.20.0
. 192.168.20.1
.
.
.
.
.
. (IPs that you can use in this network)
.
.
. 192.168.20.126
Broadcat IP is :192.168.20.127

broadcast means all hosts
like a broadcast message you tell everybody

in your example, using a mask of 255.255.255.128 is not logical because of the formula 2 to the nth power - 2, where n represents the number of masked bits (in this case 1). so 2 to the 1st power is 2, minus 2 is zero, thus leaving you with no subnets. your 4th octect would have to at least have a value of 192 to allow for 2 subnets.

However, some of the newer devices do recognize the zero's net, but I would play it safe and not try it.