Enterasys is suing LAN switching rivals Extreme Networks and Foundry Networks for patent infringement.

Enterasys filed a lawsuit this week claiming that Extreme and Foundry are infringing on six Enterasys patents involving virtual LAN (VLAN) and multi-protocol routing technologies, as well as "several other networking technologies," according to a company statement.

Enterasys did not say what damages it is seeking in the suit, filed in U.S. District Court in Massachusetts.

Earlier this month, Enterasys announced plans to shut down operations in Rochester, where the firm's former parent company Cabletron was founded in 1983. The company plans to move 200 employees from New Hampshire to its Andover headquarters. In May, the company said it will cut 300 jobs, or around 30 percent of its workforce after revenue fell short of expectations in the first quarter of 2005.

Foundry and Extreme accounted for 2.9 percent and 2.7 percent of the US$13.9 billion worldwide Layer 2-7 Ethernet switch market in 2004, while Enterasys' share of the market was 1.6 percent, according to research firm In-Stat. Cisco was the market leader with 68.6 percent of all switch revenue.

In May, a lawsuit brought by Lucent against Extreme ended when a court sided with Extreme on four out of five disputed patents. Extreme paid only US$274,990 of the US$16.4 million in damages Lucent sought. The patents involved technology for voice/data convergence and security claimed by Lucent.