A while back, I had to replace my old Linksys router with a newer one—the old one maxed out well below my FIOS connection’s 15Mbps limit. (Verizon supplied an ActionTEC router, which worked quite well, but whose admin interface I hated.) So I purchased a BEFSR41 version 4.1, which is just a newer version of the same router I already owned.
But after the switch, iPhoto and iTunes sharing no longer worked between my Macs, or with my Apple TV when it arrived. The symptoms were simple: I couldn’t see a shared library on my Mac Pro from any other machine in the house, nor could other machines see other shared libraries. It was like the shared service simply didn’t exist.
I could work around the issue by putting one machine in the so-called DMZ, but that’s far from an ideal solution. Not only does it open that one machine up to direct access from the Internet, it also allowed only that one machine to share libraries. I wanted a solution that allowed any Mac to set up a shared iPhoto or iTunes library that could be seen by the other Macs.
I posted for help in some of the various online forums, but didn’t get anything other than “yea, me too!” So I set about some serious Web digging, and eventually stumbled on this thread in the Apple Discussions forum, where I found the solution.
And that solution is this: If you’ve got a Linksys router and you can’t see shared iPhoto or iTunes libraries, open your router’s Security page. Down near the bottom, you’ll see Filter Multicast , and it will be set to Disabled. Click the Enabled radio button, then the Save Settings button. That should be the end of the problem; as soon as I made this change, sharing started working perfectly again between all my Macs and the Apple TV. Note that this fix might work for other troublesome routers, but exactly where you’ll find the setting will vary greatly from one model to the next.