Solved

Promiscuous mode

Posted on 2004-09-13
9
330 Views
Last Modified: 2006-11-17
Is there any solution for sniffing WITHOUT setting the promiscuous mode ?
0
Comment
Question by:DanLazar
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
9 Comments
 
LVL 22

Accepted Solution

by:
cookre earned 125 total points
ID: 12046070
No.  
Unless the NIC supports and is placeed in promiscuous mode, it will not report packets not intended for it.
0
 
LVL 5

Assisted Solution

by:danielsonchris
danielsonchris earned 125 total points
ID: 12046107
Promiscuous mode just means to not clear the buffer on the network card. The nature of a un-switched network is to relay packets throughout and the computer with the corresponding MAC address will accept the packet and digest it.  Turning on promiscuous mode basically tells the network card to not disregard the packet even though the MAC address does not match.  Unless you have a software application running to digest the packet it will soon be cleared out of the buffer (in the case of promiscuous mode).  Basically promiscuous mode means to put the packet into a volatile buffer such that an application such as Ethereal could digest it and display it's contents.

So the answer is no, you must have promiscuous mode turned on.  Otherwise the packet is never copied into the buffer.  Some cards have hacks that allow you to enable this if it's not enabled by default.
Regards,
Chris
0
 
LVL 41

Assisted Solution

by:graye
graye earned 125 total points
ID: 12050616
...and to make things more complicated.   The promiscuous mode has to be set both on the NIC and at the hub/switch.   Almost all hubs are now actually switches... so they too must be configured to pass all traffic to a particular port.   A low-cost hub might not even be configurable to become promiscuous.
0
Industry Leaders: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 
LVL 6

Assisted Solution

by:DominicCronin
DominicCronin earned 125 total points
ID: 12093138
It all depends what you mean by a "solution for sniffing". If all you want to do is debug some network traffic, it's very common to put some sort of proxy in between the client and the server.
0
 
LVL 22

Expert Comment

by:cookre
ID: 12320589
All of us agreed that the answer is 'no'.
0
 
LVL 6

Expert Comment

by:DominicCronin
ID: 12326949
Actually cookre, although I *do* agree that if you want to "sniff" then promiscuous mode is necessary, my suggestion was that often the problems you can solve by "sniffing" can be solved by interposing a proxy. The trouble is that word "sniff", isn't it? There's no "official" definition. Maybe we should get together and submit an RFC defining the word :-)

If sniff means "listen to network traffic not intended for your network interface", and "promiscuous mode" means "don't ignore traffic not intended for this network interface", then it's pretty obvious that you can't sniff without promiscuous mode. That still doesn't get us to a "solution" for sniffing.

What I sometimes think would be helpful would be having the option to change the question title to make it more useful to future PAQ hunters. After all, there's some useful knowledge in this thread, so it would be good to have it as a PAQ, but my worry is that the title won't help anyone to find the answers they need here.

As always - the hard part is getting the questioner to state their problem for what it is, rather than jumping in half-way towards their own perception of where the solution lies. It's unlikely that the questioner really wants to "sniff". DanLazar - if you are there - what did you really want to do?
0

Featured Post

Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Whether you’re a college noob or a soon-to-be pro, these tips are sure to help you in your journey to becoming a programming ninja and stand out from the crowd.
Although it can be difficult to imagine, someday your child will have a career of his or her own. He or she will likely start a family, buy a home and start having their own children. So, while being a kid is still extremely important, it’s also …
In this seventh video of the Xpdf series, we discuss and demonstrate the PDFfonts utility, which lists all the fonts used in a PDF file. It does this via a command line interface, making it suitable for use in programs, scripts, batch files — any pl…

734 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question