Basic Ethernet Shield / iMac setup question

Back in April, in this thread http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1236679841/15 about defaults and setting up the Ethernet shield, kg4wsv wrote:

there is sometimes a large disconnect between the networking knowledge required to successfully use an arduino ethernet shield and what the typical arduino user may know about networking

That's certainly true for me.

If I plug the ethernet shield directly into an ethernet port on my wifi router, and give it a 192.168.0.x address, it works fine - server, client, all work immediately. Unfortunately, the router is downstairs, so I really want to use the ethernet port on my mac. That's where I have trouble.

There are 3 areas I can see being able to influence:

  1. The Arduino sketch
  2. The Network pane in OSX system preferences
  3. The Sharing pane in OSX system preferences

Following most of the advice I've seen (particularly from http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1236679841/4#4 ), my settings are:

  1. Arduino:
    IP 192.168.2.200
    subnet 255.255.255.0
    gateway 192.168.2.1
  2. Network pane:
    Configure IPv4 Manually
    IP 192.168.2.3
    Subnet 255.255.255.0
    Router 192.168.2.1
    DNS Server blank
    Search Domans blank
    (My 'real' router is at 192.168.0.1, but the 2.x seems to be the way Mac internet sharing works? 0.x doesn't work any better)
  3. Internet Sharing:
    On, Share connection from Airport to Ethernet

With these settings, the WebServer and ChatServer examples work fine (i.e. I can connect to them on the iMac the ethernet shield is connected into. I can't get to them from another machine on the network, even if I change all of the IPs to 192.168.0.x, which the rest of the network uses.)

But WebClient just gives the 'connecting... connection failed error'.

I'm certain it's a EEBKAC issue...

Is there a good tutorial / troubleshooting guide anywhere, or can you suggest where I'm going wrong? I really want to see the Google result for arduino streaming up that serial monitor!

Thank you.

ps: My home network = DLink wireless router (connected to ADSL) at 192.168.0.1, Airport Extreme at 192.168.0.2