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RE: discovering network layout at layer2
From: "Aditya [ Aditya Lalit Deshmukh ]" <aditya.deshmukh () online gateway technolabs net>
Date: Mon, 9 Feb 2004 23:07:38 +0530

-----Original Message-----
From: Devrat Mittal [mailto:u02113 () cs unipune ernet in]
Sent: Sunday, February 08, 2004 5:49 PM
To: ald2003 () users sourceforge net
Subject: RE: discovering network layout at layer2

On Sun, 8 Feb 2004, Aditya [ Aditya Lalit Deshmukh ] wrote:
hi aditya,
well what i mean is apart from sniffing on my external interface to see 
what are the link layer protocol packets (Cisco DIscovery protocol) etc, 
I also need to actively determine the exact configuration of the switches 
- how many & what all hosts connected to my nearest switch & the same 

for this you need :

1. admin / root access on your machine to see all the traffic that is going through the wire 
2. if you are connected using a hub with a ethernet lan card then all you need is to put your network card in promisc 
3. if you are using switches then you have do create a braodcast storm to degrade the switch to act as a hub
4. if you are connected using a modem / isdn card then you need a tcp scanner - there are many ones one the net - this 
will not work for sniffing traffic but you will get a pretty good idea about the hosts around you


about the second & third level switch until out router is reached.

Thats what I am looking at.
Devrat Mittal

hi there as far as i know this sort of things require a 
permission from some one inchage!
thaT said, the best tool for this job would be etherreal - 
correct me if i am wrong, guys


-----Original Message-----
From: Dev [mailto:u02113 () cs unipune ernet in]
Sent: Friday, February 06, 2004 9:57 PM
To: pen-test () securityfocus com
Subject: discovering network layout at layer2

Hello ppl,  I am new to this list. Plz redirect me to another 
list if this is not the appropriate list to post to this query.   
Having read the phrack article "Fun with the spanning tree 
protocol", I was wondering as to how i could use some layer2 
protocols to my advantage to discover the network layout of my 
campus network (at layer 2).  Additionally, all equipment is 
CISCO.  Identification of my nearest switch is easily done by 
sniffing for STP BPDU packets & i did receive the STP hello BPDU 
packets on the user port that our gateway was connected to. This 
kind of packet gives me the following information:  1) How many 
more STP -capable devices are there up to the root bridge (root 
path cost)  2) The bridge & port ID & the root bridge & port ID.  
Can somebody suggest how can i find out my network topology using 
this STP protocol or some other layer2 protocol (CDP?? etc).  
regards, Devrat Mittal u02113 () cs unipune ernet in Department of 
computer Science University of Pune Pune.   

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Devrat Mittal
M.tech 2nd year
Roll no. 2002301

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