"It will be a big, expensive lawsuit," Sneath said.

Jack Gold, an analyst at J. Gold Associates in Northboro, Mass., said he believes Cisco will prevail because it has clearly been selling products with the iPhone name for a long time. "Cisco has a VoIP product that they have sold for several years, and one is the iPhone, a VoIP-based phone system, " he said. "Cisco was trying to reach an agreement with Apple for some time over the name and thought they had an agreement, but apparently [they] did not."

Apple's decision to use the name anyway "is a sign of arrogance on Apple's part, since they knew about" Cisco's use of the name, Gold said. "Apple just thinks that because they are Apple they can do anything they want."

"Of course, Cisco is going to defend itself," he said. "Cisco has as many, if not more, lawyers than Apple does. I would bet when push comes to shove, with Cisco's established brand, they are going to win. I can't see them losing. I can't see how Apple could persevere."

Rob Enderle, an analyst at the Enderle Group in San Jose, said Cisco "clearly owned" the iPhone name. "Any name search would have showed that. Cisco is monied and stubborn, Apple is monied and stubborn," Enderle said. "I think there's a pretty good chance Cisco could prevail here. It looks like someone is just saying, 'Hey, we don't want to follow the rules.' "