GeeTek1
join:2005-03-20
Del Rio, TX
| Another Noob
I can't believe this. 45 minutes on Google and this is the best answer I can find to my question, What is my Broadcast Ip, and what do I do with it ?
What is a broadcast IP address? Google answer ---->
The datagram with a broadcast IP address is received and processed by all the hosts in the local network. For example, the IP addresses 255.255.255.255, 192.9.205.255, 180.10.255.255, 10.255.255.255 are broadcast IP addresses.
I just had business edition cable broadband installed. I ordered 5 routable IP addresses. Great. I can surf like a maniac now, and am hosting my own website (I'll get around to registering a name pretty soon). Beautiful. Now what is the extra IP address named "Broadcast", and what is it for ? Oh yeah, something about "Size: /29". Checked about 12 FAQ pages with no luck. Thanks ! |
|
ponline
join:2004-03-04
presheva
| Broadcast IP is the last Ip adress of a subnet. If a computer sends something to the broadcast IP, then all the computers of that subnet respond to that request ( thats why is called a broadcast IP).
If you have /24 subnet (255.255.255.0), it means that you have 256 IP adresses (a clas C subnet) for example 111.222.123.0 - 111.222.123.255
Firs one (0) is called a network adres, and the last one (255) is a broadcast adress, those two adresses can't be used for normal operation.
If your subnet is /29 your subnet mask should be 255.255.255.248 and it means that you have 8 Ip adreses, the first one is your network adres, and the last one is the broadcast address, that leaves you 6 usable ip adresses.
Hope this helped you. |
|
GeeTek1
join:2005-03-20
Del Rio, TX
2 edits | Thanks Ponline. Yes, your explanation does indeed match my IP setup. I think that I understood what you explained about the relationship. For example, if a computer sends a ping request to the broadcast address, then it would receive 6 responses ? (assuming I had 6 computers programmed to respond to ping on my 6 IPs) ? If this is true, then I could run my Http server from one of my IPs, stream music from another, put an e-mail server on a third, and from the outside world access all 3 simultaneously at the broadcast IP ? I guess what I'm trying to understand is what practical functionality the broadcast IP performs. Thanks again for your response. |
|
IntraLink
Premium,MVM
join:2002-08-14
Utah Valley
| reply to GeeTek1
The network and broadcast IP's are not something you would consider usefull under normal circumstances. Things like routers and IP protocols use these addresses for defining routes and getting low level information around.
In other words, don't worry about it, just consider them "used" IP's; outside the range of "usefull" IP's.
Unless of course you are creating stuff like routing protocols etc... |
|
cmaenginsb
Premium,MVM
join:2001-03-19
Palmdale, CA | reply to GeeTek1
To answer your question no you won't get 6 pings back. The broadcast IP address is used for certain special kinds of broadcasts, dealing with things like ARP etc. |
|
GeeTek1
join:2005-03-20
Del Rio, TX | reply to IntraLink
AHHH finally. Relief. Thank you very much for a direct answer that means something to me. I will forget about it. I am in the process of setting up a WISP which is why I am in this forum in the first place. Thanks again for the info !! |
|
VariableARK
join:2003-03-17
USA
| reply to GeeTek1
computers use broadcast address to "find everyone else", computers use mac address to communicate, and knowbody knows anybody elses mac to start out with, so your computer sends out an arp request for the mac of such and such an ip.
actually if you ping the broadcast, depending on the operating system of the computers on your network, if you do arp-a (on windows) you will see everyone who responded,\.(used to see whos on when i dont have a sniffer on hand) |
|
GeeTek1
join:2005-03-20
Del Rio, TX
| Another Noob Happy
Interesting. I had no idea how complex TCP/Ip networking was. Still don't of course, but now I have a new horizon to peek into. This info about the broadcast IP and especially the ARP command will come in handy. Very cool of Ya'll to help me out ! Now I need to do some more fiddling and reading into this new (to me) dimension of technology. Thanks again !  |
|
bito
Premium
join:2001-10-08
Atlanta, GA
| reply to VariableARK
Re: Another Noob
said by VariableARK  : if you do arp-a (on windows) you will see everyone who responded Also helpful is "arp -d", which clears out your ARP table that holds the associations between IP addys and MAC addys. Especially helpful if you configuring a bunch of radios at one time (each with the same default IP address), or you are swapping the IP's around a lot and your network interface doesn't automatically rediscover fast enough.
Caleb |
|
