Two and a half years ago, Cisco Systems Inc. declared IP war on networking rival Arista Networks Inc.

Cisco general counsel Mark Chandler announced on his blog “official action to stop Arista’s brazen misappropriation of the fruits of our engineers’ labor.” He listed 14 patents that Arista was allegedly infringing and called out copyright infringement that was “a strategy, not an accident.”

…

Stanford law professor Mark Lemley noted that under Federal Circuit case law, a decision of invalidity from either a district court or the PTAB can render a patent unenforceable. “The patentee needs to win in both places,” he said.