Penetration Testing mailing list archives
Re: unswitched behavior of a switched network...
From: Buz Dale <buz.dale () usg edu>
Date: Mon, 16 Oct 2006 15:55:43 -0400
I can think if a couple of possibilities. 1) This is broadcast/multicast traffic. 2) The mac addresses are unknown to the switch (So it will flood to find them.) 3) The port could be a trunk or a mirror of a trunk. Buz Krugger wrote:
On 10/13/06, Jon Hart <jhart () spoofed org> wrote:Greetings, I've got a situation here that I can't quite figure out. It is well known that it is possible to cause a switched network to act like an unswitched network by flooding the CAM table. There are countless tools and documents out there that cover the offensive and defensive measures related to this issue. While this isn't Cisco's official documentation on this issue, http://xrl.us/r8k7 says: "Content-addressable memory (CAM) overflow: A CAM table is used to determine where to direct incoming frames depending on which port the incoming MAC address came from. When the CAM receives a frame with an unknown destination, the proper procedure is to flood frames within the acceptable Layer 2 domain (the proper VLAN). Hardware and software tools are available (some for free), that can flood a switch with MAC addresses. Once the CAM table limit is exceeded, switches behave differently depending on the brand of the switch." My question is, has anyone seen a situation where the same broadcast behavior occurs, but the CAM table itself is not overloaded and there is no good reason for entries to be expiring? Furthermore, even if the entries were expired, has anyone encountered situations (malicious or otherwise), where a given port will receive traffic outside of its own L2? Thanks, -jonSome router have an option of dumping all traffic to a give port, so if you are connected to the right router port you will see everything as if it was a hub. At least I already saw a router configured that way, that port that was connected to a computer that was dedicated to run snort. ------------------------------------------------------------------------ This List Sponsored by: Cenzic Need to secure your web apps? Cenzic Hailstorm finds vulnerabilities fast. Click the link to buy it, try it or download Hailstorm for FREE. http://www.cenzic.com/products_services/download_hailstorm.php?camp=701600000008bOW ------------------------------------------------------------------------
-- ---- Buz Dale buz.dale () usg edu IT Security Specialist 1-888-875-3697 Office of Information and Instructional Technology University System of Georgia ------------------------------------------------------------------------ This List Sponsored by: Cenzic Need to secure your web apps? Cenzic Hailstorm finds vulnerabilities fast. Click the link to buy it, try it or download Hailstorm for FREE. http://www.cenzic.com/products_services/download_hailstorm.php?camp=701600000008bOW ------------------------------------------------------------------------
Current thread:
- unswitched behavior of a switched network... Jon Hart (Oct 13)
- Re: unswitched behavior of a switched network... Krugger (Oct 16)
- Re: unswitched behavior of a switched network... Ron (Oct 16)
- Re: unswitched behavior of a switched network... David Swafford (Oct 16)
- Re: unswitched behavior of a switched network... Buz Dale (Oct 16)
- Re: unswitched behavior of a switched network... Jon Hart (Oct 16)
- Re: unswitched behavior of a switched network... Tim (Oct 17)
- RE: unswitched behavior of a switched network... Erin Carroll (Oct 17)
- Re: unswitched behavior of a switched network... David C. Smith (Oct 18)
- Re: unswitched behavior of a switched network... Ron (Oct 16)
- Re: unswitched behavior of a switched network... Krugger (Oct 16)
- Re: unswitched behavior of a switched network... Florian Osses (Oct 16)
- Re: unswitched behavior of a switched network... Can't dig that daddy (Oct 16)
- <Possible follow-ups>
- RE: unswitched behavior of a switched network... Michael Scheidell (Oct 16)