I recommend you to use Flash Media Live Encoder. Using FMLE you will be able to get the input from your IP camera and then stream it to Flash Media Server.
Steps to configure the camera with FMLE
1. Launch FMLE.
2. In video, Device option choose the Ip camera.
3. Stream to Flash Media Server, FMS URL - rtmp://
With this FMLE will capture the frames from the IP camera and publish a stream to Flash Media Server.
Link to FMLE product page - http://www.adobe.com/products/flashmediaserver/flashmediaencoder/
Let's all be more specific. I think that each party seems to be confused as to what the other means by "IP Camera". Let me translate.
IP Camera is something like an Axis P1346 and uses rtsp to stream h.264 and AAC.
IP Camera DOES NOT MEAN the Logitech Web Cam attached to the computer running Flash Media Live Encoder.
Thus, in this case there is no "IP Camera" in the video device drop down.
But Wowza Media Server is capable of doing just what you are asking.
Now I think Axis has a video capture driver that you could install on the machine with the Adobe Media Encoder.
That may make it work and show up as a device in Flash Media Live Encoder.