RE: arpwatch

["ted koenig" <tkoenig () lf-mail com>]

I would think the only real purpose of doing arpwatch is to prevent apr, arp
poison routing, and on a network of any major size/traffic volume you will
notice a significant slowdown if somebody is up to that.  Basically it
effectively turns a switched network into a hubbed one by making everyone
route through one machine, so that guy can sniff stuff out.   For the most
part, switches hamper the average sniffer.

Ted Koenig
LaFrance Corp.
Network Administrator


-----Original Message-----
From: John T. Hollyoak [mailto:john () mail isc rit edu] 
Sent: Thursday, September 11, 2003 3:05 PM
To: security-basics () securityfocus com
Subject: Re: arpwatch


Tomas / Zidan,

I just wanted to respond and add some information and ask a few
questions....

a) What switches (that you are aware of) leak?  Do you have any other
information about this? links?
b) port mirroring or a monitor port, is the way to go.  Check out the
monitor command on the cisco switches, for an example of how to do this.
Basically maps a range of ports, to a single port, for the purposes of
monitoring (i've actually used it for an IDS before).
c) Using a tool within the Dsniff package, called "macof" ... this can be
accomplished, simply by blasting the CAM table (Content Addressable Memory)
with alot of addresses.  The device will either fail open, or fail closed...
meaning the basically turn into one big collision domain (hub).

arpwatch is partially useful, if you have a small network.  Anything that
has a constant amount of ARP requests/replies .... will just create alot of
junk.

What are you trying to accomplish by using ARPwatch?  Perhaps there is a
better tool available .....

John Hollyoak


----- Original Message -----
From: "Tomas Wolf" <tomas () skip cz>
To: "zidan" <zidan00 () fastmail fm>
Cc: <security-basics () securityfocus com>
Sent: Thursday, September 11, 2003 7:33 AM
Subject: Re: arpwatch


> my 2c --
> a) some switches horribly leak :-)
> b) port mirroring would be the best bet (managable switches necessary)
> c) some under heavy load work like hubs (flood it)
>
> good luck - T.
>
> zidan wrote:
>
> > hello,
> >
> > I have recently installed arpwatch on one of our servers. I 
> > understood arpwatch "learns" arp replies, but since arp replies are 
> > destined to a specific MAC and this is a switched network, how can 
> > arpwatch see all arp replies ?
> >
> >
> > -Z
>
>
>
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---------------------------------------------------------------------------
Captus Networks 
Are you prepared for the next Sobig & Blaster? 
 - Instantly Stop DoS/DDoS Attacks, Worms & Port Scans 
 - Precisely Define and Implement Network Security 
 - Automatically Control P2P, IM and Spam Traffic 
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---------------------------------------------------------------------------
Captus Networks
Are you prepared for the next Sobig & Blaster?
 - Instantly Stop DoS/DDoS Attacks, Worms & Port Scans
 - Precisely Define and Implement Network Security
 - Automatically Control P2P, IM and Spam Traffic
FIND OUT NOW -  FREE Vulnerability Assessment Toolkit
http://www.captusnetworks.com/ads/42.htm
----------------------------------------------------------------------------