Multiple Cisco networking products allow remote attackers to cause a denial of service on the local network via a series of ARP packets sent to the router's interface that contains a different MAC address for the router, which eventually causes the router to overwrite the MAC address in its ARP table.
https://exchange.xforce.ibmcloud.com/vulnerabilities/7547
http://www.securityfocus.com/bid/3547
http://www.kb.cert.org/vuls/id/399355
http://www.cisco.com/warp/public/707/IOS-arp-overwrite-vuln-pub.shtml