Juniper Networks has made a $2 million investment in Packet Design, a developer of routing analysis and optimization software, as part of Packet’s Design’s $12 million fourth round funding.

Juniper is Packet Design’s first “strategic investment partner,” according to the private company. Past investors Advanced Technology Ventures, Masthead Venture Partners and Mayfield Fund are lead investors in the round.

The funding will be used to expand the company's network management product line and grow its international sales force, and is expected to carry the company to a break-even cash flow by the end of 2009, Packet Design says. The company says it grew 80% from 2006 to 2007 and has 300 customers worldwide.

Juniper, in a statement, said Packet Designs is “an innovator in both routing and traffic analysis,” and the company’s software will help Juniper customers manage large and complex next-generation networks.

The new funding brings Packet Design's total financing to $44.5 million.

Packet Design was founded in March 2003 by former Cisco CTO and serial entrepreneur Judy Estrin and former Cisco Chief Scientist Van Jacobson.