What is a broadcast ip?

snocked · 01-26-2003, 11:26 PM

I was looking at my ifconfig output and I'm trying to setup a network. So what is a broadcast ip?

DavidPhillips · 01-26-2003, 11:42 PM

braodcast ip would be your network with 255 for the last octet

ip 192.168.0.1, netmask 255.255.255.0, network 192.168.0.0, broadcast 192.168.0.255

snocked · 01-27-2003, 01:02 AM

Ok thanks a bunch.

jdc2048 · 01-27-2003, 04:06 AM

What David stated will work on a non-subnet'd class c network. If you subnet that, then it would be the highest IP in the subnet (i.e. network is from 192.168.1.1 to 192.168.1.32, then 32 is the last octet). I figure he knows that, he was just trying to keep it simple.

baldy3105 · 01-27-2003, 11:13 AM

umm, .32 would be the network address of the next subnet

192.168.1.1 with a 255.255.255.224 mask as in your example would give you a broadcast address of 192.168.1.31

Basically the broadcast address for any subnet is the value you get when you set all the host bits to 1.

In the above example the .224 mask would give you 3 network bits and 5 bits for the host address. Set all these host bits to a 1 and you get 31.

Sorry to be picky :-)

jdc2048 · 01-27-2003, 05:44 PM

You are right sir, I stand corrected.

DavidPhillips · 01-28-2003, 07:06 AM

it can get a lilttle complicated if your on a subnetted network

you can use this

http://www.a-plus.net/Useful_Netmask.htm

decates · 01-28-2003, 09:56 AM

And in case you STILL want to know what a broadcast ip is...

Quote:

Broadcast is the term used to describe communication where a piece of information is sent from one point to all other points. In this case there is just one sender, but the information is sent to all connected receivers.

So the broadcast address can be used to send a message to all the computers connected to a LAN (e.g. ARP uses it to send address resolution queries - try 'tcpdump' and you will get the idea)

'Hey, what is a car?'
'It's a Ford or a Toyota or a Rover... '
'Umm, thanks a bunch.'