Today I had a major incident in our LAN.
One of our wi-fi Vlans that is routed on Cisco L3 3750 switch has been paralysed. Devices were able to connect but when You try to ping them 75-90 % of the packets were lost.
After few hours it turned out that two linksys wifi-eth. converters were accidentally linked together with it's eth. interfaces. The effect was that entire Vlan within entire Cisco switched network was almost cutted off.
On our L3 Cisco switch logs I saw plenty of entries like this:
14w0d: %IP-4-DUPADDR: Duplicate address xxx.xxx.xxx.xxx on Vlan6, sourced by 0004.23aa.9eb5
How two little devices linked together could paralyse entire Vlan ?
Do You know how to protect from such situations in the future ?