Start iTerm and then open the Bookmarks windows. The window should look something like this:
At the bottom of the Bookmarks windows is a button with a plus sign in it. Click this to add a book mark and configure as shown here
Now repeat this for as many routers as you are likely to have in your biggest lab. For my MacBook Pro with 4GB RAM this is more than 20 routers so I have listed 20 bookmarks.
Now close the Bookmarks window, and select new from the toolbar in the main windows and extend in to the new menu that you have just created, and then select the Open All option – as shown here:
iterm will open all of the sessions. When there is nothing to connect to, they will just shutdown and not be visible on the toolbar. This screenshot shows active sessions for a lab that has eight routers in it.
One of the great features of iTerm is the ability to drag the tabs into new windows. Just click and hold the tab and then drag it off the session toolbar to create a new windows
Once you have all the Windows open, you can switch between the first nine windows by using Command+1, Command+2, Command+3 etc. This makes switching between the windows very quick.
If you decide to open all as separate windows this does not work.
Hope this helps to make your life a bit simpler.