Cisco Systems has recalled about 11,000 hardware add-ons called "modules" used in its popular Catalyst 5000 switches, according to the company. A Cisco spokesman said 14 businesses using the networking equipment have reported cases where the switches have shorted out. The 10-megabit Ethernet-based add-on modules are used to connect computers on a network. Only about 11,000 out of the 75,000 that have been shipped have the problem, a Cisco spokesman said. The networking firm alerted customers about the recall in early December, he said.