Connection Problems when Ethernet Cables are Looped into Switches
We provide 4 port switches for students in dorm rooms. There are usually two or three students per room. Sometimes students plug in the Ethernet cables incorrectly. A couple of times this past semester, different students have looped Ethernet cables into their switch. (For example, one end is in Port 2 and the other end is in Port 3.) We have found that these students are not trying to be malicious, but they don't realize what they are doing (and sometimes are just trying to "clean up" cables that are around their room). However, when they loop a cable, it generates quite a bit of traffic on the network. In certain cases, it has bogged down and halted the Internet connection for an entire wing of student computers.
Does anyone have any suggestions on how we can prevent this problem? Is there a way to temporarily "fill in" empty switch ports? It is cost prohibitive for us to run all new cabling throughout the old dorm buildings. Any suggestions would be appreciated.
You really need to properly configure spanning tree options out at those access switches. All switches have different options, here are the features you should research to fix your problem if you run newer Cisco switches:
Portfast - puts ports automatically into forwarding, it's fast and helps with DHCP problems
UDLD - loop detection feature that shuts down a portfast switchport when a loop is detected as coming from a hub. It will require someone to "no shut" the port when it happens before it can be usable again if there is not a error disabled recovery timer set manually.
