RE: How to find a changing IP on ethernet network

["David Gillett" <gillettdavid () fhda edu>]

  If you're using Cisco Catalyst switches, this feature is
called "port security".  Enable it, tell it how many MAC
addresses to allow per port, and whether, when this number 
is exceeded, to issue an SMTP trap to your Network Management 
package, or shut down the switch port.
  Of course, if you're using some other equipment, you need
to find out what features, if any, that equipment offers.

David Gillett


> -----Original Message-----
> From: Bhavani Suresh [mailto:bhavani.suresh () adnoc-dist co ae]
> Sent: Wednesday, February 25, 2004 2:36 AM
> To: Gideon T. Rasmussen, CISSP, CISM, CFSO, SCSA;
> security-basics () securityfocus com
> Subject: RE: How to find a changing IP on ethernet network
>
>
>
> Following up this..i want to know at the network level any 
> software can
> bind the MAC Addresses to the ports (and to take current MAC Addresses
> in the network automatically)so that no new ip address can be 
> allocated
> without the consent of the network admin. This will also 
> ensure security
> so that non one just plugs in a pc or laptop..
>
> Any idea..
>
> -----Original Message-----
> From: Gideon T. Rasmussen, CISSP, CISM, CFSO, SCSA
> [mailto:lists () infostruct net] Sent: Saturday, February 21, 2004 20:12
> To: security-basics () securityfocus com
> Subject: Re: How to find a changing IP on ethernet network
>
>
>
>   Ivan,
>
> This is an interesting situation. Here are a few possible 
> ways to address it:
>
> 1. Send an e-mail to the user community explaining the 
> problem and asking them to leave their IP address 
> configurations alone.
>
> 2. In case you don't know, as the new system boots it 
> announces its IP address to the network. If another system 
> already has that IP address, it will reply and the new system 
> will shut down the interface running the duplicate IP.
>
> a. From the new system, run the arp command (arp -a).
>
> C:\> arp -a
>
> Interface: 192.168.2.100 --- 0x20002
>   Internet Address      Physical Address      Type
>   192.168.2.1           00-06-25-c0-93-65     dynamic
>
> This will list the IP address and associated MAC (hardware) 
> address (e.g. 00-06-25-c0-93-65).
>
> b. Now all you need to do is find out which system has that 
> MAC address:
>
> C:\> ipconfig /all (output abbreviated)
>
>         Physical Address. . . . . . . . . : 00-06-25-c0-93-65
>
> 3. You could also use tcpdump or windump 
> (http://windump.polito.it) to sniff the network traffic for 
> that specific IP and view the resulting dump file with 
> Ethereal (http://www.ethereal.com). This is a bit advanced 
> for the average user.
>
> If you have any additional questions, please do not hesitate 
> to contact
> me.
>
> Kind regards,
>
> Gideon
>
> Gideon T. Rasmussen
> CISSP, CISM, CFSO, SCSA
> Boca Raton, FL
> gideon () infostruct net
>
> National Security Awareness Day - September 10, 2004 - Are you aware?
>
> Subject: How to find a changing IP on ethernet network
> From: Ivan Andres Hernandez Puga <ivan.hernandez () globalsis com ar>
> Date: Fri, 20 Feb 2004 11:54:29 -0300
> To: security-basics () securityfocus com
>
> Hello. I have a client with a simple Ethernet network with 
> HUB's connecting and there is one person that is changing 
> it's IP and creating
>
> conflicts. What would you do to track down that person? i 
> mean, to find who does that?
>
> Thanks!
>
> Ivan Hernandez
>
>
>
>
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