See this for route flapping. See the instability section on the BGP page. Link flap means that the interface continually goes up and down in a Cisco Switch. The interface is put into the errdisabled state if it flaps more than five times in 10 seconds. The common cause of link flap is a Layer 1 issue such as a bad cable, duplex mismatch, or bad Gigabit Interface Converter (GBIC) card. Look at the console messages or the messages that were sent to the syslog server that state the reason for the port shutdown Also check by post at ITKE for more details

<a href="http://searchtelecom.techtarget.com/feature/BGP-essentials-The-protocol-that-makes-the-Internet-work">See this</a> for route flapping. <a href="http://searchtelecom.techtarget.com/definition/BGP">See the instability section on the BGP page</a>. Link flap means that the interface continually goes up and down in a Cisco Switch. The interface is put into the errdisabled state if it flaps more than five times in 10 seconds. The common cause of link flap is a Layer 1 issue such as a bad cable, duplex mismatch, or bad Gigabit Interface Converter (GBIC) card. Look at the console messages or the messages that were sent to the syslog server that state the reason for the port shutdown Also check by <a href="http://itknowledgeexchange.techtarget.com/network-technologies/what-is-the-link-flap-error-in-cisco-switches/">post at ITKE</a> for more details