A week ago VMware said it was buying Nicira for $1.26 billion for its cloudy software-defined network virtualization.

Monday morning Oracle said it's buying Xsigo Systems for its cloudy software-defined network virtualization.

Oracle's not saying what it's paying and it's unclear how much funding the eight-year-old company took in from VCs like Kleiner Perkins, Khosla Ventures, Greylock Partners and North Bridge Venture Partners.

Like the Nicira acquisition, Xsigo in Oracle's hands threatens Cisco and Juniper.

Xsigo, which has worked with Oracle in the past, is more established than the fledging Nicira. Xsigo's stuff is supposed to simplify cloud infrastructure and operations by letting customers connect any server to any network and storage dynamically and flexibly, resulting in increased asset utilization and application performance while reducing cost.

Its 300 enterprise customers include British Telecom, eBay, Softbank and Verizon.

Oracle means to use the technology with Oracle VM for server virtualization to deliver a complete set of virtualization capabilities for cloud environments. Presumably that means in its Exadata, Exalogic and Exalytics machines.

According to a statement from Oracle EVP of systems John Fowler, "The proliferation of virtualized servers in the last few years has made the virtualization of the supporting network connections essential. With Xsigo, customers can reduce the complexity and simplify management of their clouds by delivering compute, storage and network resources that can be dynamically reallocated on-demand."

Oracle has been buying cloud companies lately.

See http://www.oracle.com/us/corporate/acquisitions/xsigo/general-presentation-1720526.pdf.