If you're supposed to keep your friends close and your enemies even closer, I suppose it makes sense to keep your consolidated subsidiaries right next to you. While IDT (NYSE:IDT) has always maintained voting control over VoIP company Net2Phone (NASDAQ:NTOP), the company has now taken the final step and announced a tender offer for the outstanding Net2Phone common stock it doesn't already own.

The deal offers $1.70 per share in cash to Net2Phone holders -- about a 21% premium to Tuesday's closing price. Given that Net2Phone was trading close to the level of its book value and cash per share, that 21% premium isn't quite as robust as it might initially sound -- not if you believe Net2Phone has technology and/or patents that are worth anything.

Interestingly, the stock was actually trading above the $1.70 offer price in pre-market trading on Thursday. I find that puzzling. IDT's voting control over Net2Phone means that a rival offer can't possibly succeed unless IDT chooses to permit it. Why would IDT bother with a tender offer now if they were willing to let an outsider come in and buy it?

Net2Phone's return to the fold should create some accounting benefits for IDT. The company can largely eliminate Net2Phone's operating expenses, and IDT should also get access to Net2Phone's net-operating-loss tax carryforwards.

Of course, the biggest benefit will come if the VoIP business really takes off in Net2Phone's favor. Few American providers have stepped up to join the company's recent efforts in cable telephony. Firms such as Comcast (NASDAQ:CMCSA) and Time Warner (NYSE:TWX) seem more interested in building their own approaches than partnering with the likes of Net2Phone.

Whether or not that changes, it would appear by my calculations that when cash is stripped out, IDT is paying only about $23 million to bring this business fully in-house. That's not a hefty price for what may amount to a long-term call option on the residential VoIP market.

For more information on IDT and Net2Phone:

Fool contributor Stephen Simpson held no financial position in any stocks mentioned at the time of publication.