Bugtraq mailing list archives
Re: DoS of LAN via D-Link switches
From: "Tarmo Mamers" <tarmo () pobox com>
Date: Wed, 30 Mar 2005 00:29:24 +0300
From: Frank Bures [mailto:lisfrank () chem toronto edu] Sent: Tuesday, March 29, 2005 4:41 AM
When user connects the same patch cable to two ports of the switch, the switch will ultimately bring down hierarchically higher branches of the LAN.
Ours is a rather large LAN. One part of it is served by Extreme Networks switches. None of the SGI machines behind these switches were affected by the short. In fact no adverse effects were observed in that part of the LAN.
This is natural behaviour of Ethernet ("natural" being dependent of your network design, of course :) and has nothing to do with D-Link or any other manufacturer. Some switches offer automatic port disabling feature if BPDU is received on a port defined as access port. All workstation ports should be defined as access ports for this to work. Workstations are not taking part of any Spanning Tree and they shouldn't generate any BPDUs and thus BPDUs shouldn't come into the switch from any access port. When you interconnect two switch ports defined as access ports, BPDUs generated by the switch reach another access port and trigger the disabling feature. This works in case or a single switch as well as between different switches as long as all your switches are Spanning Tree enabled. How the "short-circuit" affects specific switches depends how their unknown frame forwarding is configured and where they stand in a multi-tier switch topology.
In my opinion, a switch should be immune to this admittedly insane manipulation. Otherwise, one can DoS the entire network just by shorting two RJ-45 network outlets in one's office together.
Switches _are_ immune to insane manipulation if configured correctly. Excluding plugging out the power cord, unfortunately... -tarmo-
Current thread:
- DoS of LAN via D-Link switches Frank Bures (Mar 29)
- RE: DoS of LAN via D-Link switches David Gillett (Mar 29)
- Re: DoS of LAN via D-Link switches Tarmo Mamers (Mar 29)
- Re: DoS of LAN via D-Link switches Neil Watson (Mar 30)
- Re: DoS of LAN via D-Link switches Joel Maslak (Mar 31)
- Re: DoS of LAN via D-Link switches Scott Nelson (Mar 31)
- Re: DoS of LAN via D-Link switches Tarmo Mamers (Mar 29)
- RE: DoS of LAN via D-Link switches David Gillett (Mar 29)