I think a better way to accomplish this would be to use one account, and define a view in Analytics that includes external IPs. That's the way we're handling this need.

In a nutshell:

In Analytics, Administration, select the account and property you need to filter. Create a new view (e.g. External Only). Select Filters, and add one that excludes IP addresses starting with the value corresponding to your private network range (e.g. 10 or 192.168).

Once you have the view saved and selected, go back to reporting and you should only be seeing external hits. If you need to be able to view internal only, you can easily set up a view for that too.

Jamie

I think the IP address filters only work on a go-forward basis, so you'll need to wait for new data to be captured by Google before you can see it in the reports and graphs.

When I made my first reply, I had to go through the process again myself to remember the sequence of steps. At the time, I created a new view for our internal users (10.*). I just went back today and selected the account, property, and internal users only view and saw that activity has been logged in that view, starting on the date I created it.

At this point, I don't have any other advice for you, other than to spend some time going through the Analytics Academy training sessions. Those helped me to understand and use Analytics much better (it's where I learned about custom filtered views).

Jamie