Time Machine from networked Mac?

Is it at all possible to setup Time Machine so that it backs up to a disk image on my external Mac?

Here's my setup:

• My MBA which will be backed up
• MBP which is connected to the wireless network
• External drive connected to the Mac which I want the data to be backed up to
• MBP is running Snow Leopoard
• MBA is running ML

Is this possible? I could also connect this drive to my router, but as of right now, it doesn't look like it's seeing it.

This tutorial should be able to help you:

http://www.reasonablyopinionated.com/2011/11/time-machine-backups-to-drive-on.html

I just tried it and it worked for me. Not sure how reconnects will go after a reboot or something, but it shouldn't be that difficult to get working again.

There is the tmutil setdestination command that you can use in Mountain Lion, even when the GUI is not showing the unsupported drive.

Stole the answer from this blog post:

http://roadglide03.blogspot.co.il/2012/08/using-smb-share-in-mountain-lion-for.html