Cisco has reportedly made an offer to acquire internet phone firm Skype before it completes its planned initial public offering, according to Techcrunch.

Techcrunch said the rumor came from one of its more reliable sources but it has not been able to confirm anything. If it’s true, the deal could be a big one as Skype is gunning for a valuation of $5 billion. Techcrunch said that Google was also rumored to be considering an offer for Skype, but antitrust concerns may have derailed that bid. We’ll offer more details as they come in. Josh Silverman, chief executive of Skype, is pictured.

One of my own sources confirmed that Cisco has made the offer and it is serious about combining Skype’s internet communications service with its own WebEx collaboration tools.

Cisco is the world’s biggest internet networking equipment firm with plenty of presence in internet applications. So there is some reason for Cisco and Skype to be married. But after the surprise acquisition of security firm McAfee by Intel, I suppose that just about any combination of tech companies is possible.

On August 9, Skype filed for an IPO. That filing came after eBay finalized the sale of 70 percent of the company in November 2009 to an investment consortium led by Silver Lake Partners. It included participation from Canada Pension Plan Investment Board, venture firm Andreessen Horowitz, and Joltid — the peer-to-peer technology company founded by Skype’s founders Niklas Zennström and Janus Friis. The sale left eBay with 30 percent of Skype, Joltid with 14 percent, and the rest of the investment group with the remaining 56 percent. The deal valued Skype at $2.75 billion, and eBay was paid $1.9 billion in cash, and received a note from buyer worth $125 million.

To make the deal happen, eBay first had to settle some longstanding lawsuits with Skype’s founders – drama that mostly centered around the Joltid-owned peer-to-peer technology underneath Skype. Joltid was transferred to Skype as part of the deal, and it was partially what led to the founders receiving 14 percent of the company.

In addition to the IPO announcement, Skype’s filing revealed some interesting details about the company and its user base. For one thing, it’s profitable. Skype snagged $13 million on $406 million in revenues for the first six months of 2010. Looking at it with non-GAAP metrics, Skype generated $115.8 million in profits in that time.

The company says it has 560 million registered users, with 124 million using it every month. 8.1 million of those users pay an average of $96 a year for the service.