EDIT 18/05/2011: Thanks for your answers, bridge mode IS the solution in most cases for this problem, but I can't use it because it breaks my web server. I am now looking at setting up a specific route as a solution and thats taken care of in a new question here: Setting up a route between WLAN and LAN on a Checkpoint 500w? Please help if you can. Save my sanity!
(Please note, this question has been heavily edited!)
This was originally a question about getting iTunes Home Sharing to work - using the iPhone (or an iPad) as a remote to control iTunes on a desktop computer. The remote device, in this case an iPhone, is on a wireless network and the desktop PC is on a wired network.
Both wired and wireless networks are handled by a single device which is an all in one business-class firewall and router, a checkpoint safe@office 501w.
The problem was trying to pair 'remote' with 'iTunes' resulted in, well - nothing. No log entries, the software either side saying nothing about anything, just a complete blank.
I found a solution - described in the edit below - the device was throwing up a firewall to protect the wired network from the wireless one, which makes sense if you think about it - to get on my wired network you have to be in my house, so its a good chance I either know who you are or you're stealing my hardware anyway...
You can technically get on the wireless from outside, though you'd have to get around the mac address filtering which I hear is not actually impossible, so it makes sense to firewall the main wired network from that access.
I found 'bridge' mode and enabled it and it all worked straight away, but I quickly turned it off again - I don't want a full, perma-bridge between the wireless and wired if at all possible, I just want a bridge or route from the iPhone or iPad to the computer.
So thats now the question - not how to get it working, thats been solved - but how to get it working without potentially leaving a gaping network security hole?
OK - It works, except I think I may have enabled it to work at a cost of some other security. I was looking around the firewall settings, specifically wireless network and had the option to either configure it in "Firewall Mode" or "Bridge Mode" - the explanation being:
To protect your wired LAN from being accessed by wireless users, select Firewall Mode. If you prefer to grant full access from the wireless LAN to the LAN, bypassing firewall protection, select Bridge Mode.
I probably should have spotted this about 6 months ago... switching to bridge mode works. HOWEVER, I really would prefer not to allow broad access between Wifi and Wired, i'd rather just allow access between the two as needed... I do use mac address control and its unlikely that anyone who lives within range is a hacker hellbent on accessing my files, but i'd rather stick with good practice.
So the question should now be - how can I emulate this bridge mode ONLY FOR device(s) I specify?