Open the shapesheet and find the Miscellaneous Section. Enter the information in the comment cell. Y0u can insert other fields, like a custom property (or properties)

John...   Visio MVP - Visio.MVPs.org

Thanks! I  entered comment in =INDEX(0,INDEX(0,MASTERNAME(),":"),"my comment ") and save it but nothing appears on the shape.  

What are you expecting this formula to do?

John...   Visio MVP - Visio.MVPs.org

I have large network diagram and I do not have space in the drawing to display server info. So I was thinking if I move my cursor on the particular server it will pop up window that display the server info.  

I was referring to what you expected
=INDEX(0,INDEX(0,MASTERNAME(),":"),"my comment ")
to evaluate to. Index just returns an integer, so what were you expecting to be placed in the Comment Cell?

You can create a custom property in the Shape and then when you edit the shapesheet, enter a reference to the cell within the custom property row you create for an IP address.
When you hover over a shape, the content of the Coment cell is displayed.

John...   Visio MVP - Visio.MVPs.org

I was trying to put some text inplace of "my comment". Can you please elaborate how to create custom property.Also does it works if I convert visio into html format as well.  

To create a custom property (it is called shape data in 2007), go to the View menu and make sure Shape Data Window is selected. There should be a Shape Data window on the page and it will show the shape data (custom property) for the selected shape. When the shape is selected, right click the shape data window and choose "Define Shape Data...". Change the label to IP Address, leave the Type as string and set the value to the IP address.

Before I continue to explain how to link the comment cell to this shape data, I must warn you that if you are planning on changing a lot of shapes, you should be working on the shape's master. Once the master is changed, all the occurrences will inherit the new feature.

Open the shapesheet for the shape and find the Miscellaneous section and the Comment cell. Select the Comment cell and then scroll back to the Shape Data section. Click on the value cell. This will place a formula in the Comment cell that references the value in the Shape Data record. Now any time you hover over the shape, a balloon will show containing the IP Address.

If you need to change the IP Address, you can open the shape data window for each shape and change the shape data. You can also link the shape data to an external database or Excel spreadsheet.

John...   Visio MVP - Visio.MVPs.org