LinuxQuestions.org
Visit Jeremy's Blog.
Go Back   LinuxQuestions.org > Forums > Linux Forums > Linux - Networking
User Name
Password
Linux - Networking This forum is for any issue related to networks or networking.
Routing, network cards, OSI, etc. Anything is fair game.

Notices


Reply
  Search this Thread
Old 01-23-2018, 03:01 AM   #1
hack3rcon
Senior Member
 
Registered: Jan 2015
Posts: 1,432

Rep: Reputation: 11
Post What is the broadcast address?


Hello.
When I get a properties from my NIC then I see a "Broadcast Address", What is it?


Thank you.
 
Old 01-23-2018, 04:23 AM   #2
ferrari
LQ Guru
 
Registered: Sep 2003
Location: Auckland, NZ
Distribution: openSUSE Leap
Posts: 5,781

Rep: Reputation: 1139Reputation: 1139Reputation: 1139Reputation: 1139Reputation: 1139Reputation: 1139Reputation: 1139Reputation: 1139Reputation: 1139
A broadcast address is the address used to broadcast packets to every client on the LAN. The broadcast address is always the highest number possible in a particular subnet.
 
Old 01-23-2018, 02:10 PM   #3
Habitual
LQ Veteran
 
Registered: Jan 2011
Location: Abingdon, VA
Distribution: Catalina
Posts: 9,374
Blog Entries: 37

Rep: Reputation: Disabled
A broadcast address is a logical address at which all devices connected to a multiple-access communications network are enabled to receive datagrams. A message sent to a broadcast address may be received by all network-attached hosts.[1]
 
Old 01-27-2018, 09:03 AM   #4
hack3rcon
Senior Member
 
Registered: Jan 2015
Posts: 1,432

Original Poster
Rep: Reputation: 11
I know broadcast address is 255.255.255.255 but please see my attached photo.
Attached Thumbnails
Click image for larger version

Name:	Lan-.png
Views:	277
Size:	38.0 KB
ID:	26815  
 
Old 01-27-2018, 09:57 AM   #5
lazydog
Senior Member
 
Registered: Dec 2003
Location: The Key Stone State
Distribution: CentOS Sabayon and now Gentoo
Posts: 1,249
Blog Entries: 3

Rep: Reputation: 194Reputation: 194
The network you are on is setup as follows:

Network: 172.25.1.64/26
Broadcast: 172.25.1.127
HostMin: 172.25.1.65
HostMax: 172.25.1.126
Hosts/Net: 62

You NIC setup looks correct provided the gateway is 126.

In a subnet you have the network address, which is the first IP Address, that can never be used and a broadcast address, which is the last IP Address, that also can never be assigned. That is why yopu see when referencing subnets are N-2 for usable addresses.

Take for example your subnet /26. That has 64 total addresses but only 62 are usable because the network identifier (172.25.1.64) and the broadcast (172.25.1.127) cannot be used leaving 65-126 usable. Looks like the network admin has chosen 172.25.1.126 as the gateway for this network.
 
1 members found this post helpful.
Old 01-27-2018, 10:08 AM   #6
michaelk
Moderator
 
Registered: Aug 2002
Posts: 25,592

Rep: Reputation: 5880Reputation: 5880Reputation: 5880Reputation: 5880Reputation: 5880Reputation: 5880Reputation: 5880Reputation: 5880Reputation: 5880Reputation: 5880Reputation: 5880
If you read the Wikipedia article 255.255.255.255 is a special definition. In addition from the same article...
Quote:
The broadcast address for an IPv4 host can be obtained by performing a bitwise OR operation between the bit complement of the subnet mask and the host's IP address. In other words, take the host's IP address, and set to '1' any bit positions which hold a '0' in the subnet mask. For broadcasting a packet to an entire IPv4 subnet using the private IP address space 172.16.0.0/12, which has the subnet mask 255.240.0.0, the broadcast address is 172.16.0.0 | 0.15.255.255 = 172.31.255.255.
As stated it is the highest possible address in the subnet. From the image posted your subnet is defined as
172.25.1.64/26 (255.255.255.192) broadcast 172.25.1.127

This means the range is 172.25.1.64 - 172.25.1.127. Since you can not use lowest or highest address i.e. one defines the subnet, the other the broadcast, the number of possible hosts is 62 i.e. 172.25.1.65 - 172.25.1.126.

Always late...

Last edited by michaelk; 01-27-2018 at 10:09 AM.
 
  


Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off



Similar Threads
Thread Thread Starter Forum Replies Last Post
change destination ip address to broadcast address by iptables kikilinux Linux - Networking 3 08-26-2014 11:50 AM
Broadcast address estratos Linux - Networking 7 03-08-2007 09:02 AM
What can cause a broadcast address change? ca346734 Linux - Networking 2 10-21-2005 04:03 PM
how to get ip address, broadcast address, mac address of a machine sumeshstar Programming 2 03-12-2005 04:33 AM
question about network address and broadcast address yuzuohong Linux - Networking 1 09-18-2002 11:47 AM

LinuxQuestions.org > Forums > Linux Forums > Linux - Networking

All times are GMT -5. The time now is 08:01 AM.

Main Menu
Advertisement
My LQ
Write for LQ
LinuxQuestions.org is looking for people interested in writing Editorials, Articles, Reviews, and more. If you'd like to contribute content, let us know.
Main Menu
Syndicate
RSS1  Latest Threads
RSS1  LQ News
Twitter: @linuxquestions
Open Source Consulting | Domain Registration