Local DNS entries
I'm guessing this is a really noobie question to be asking but I don't do much with DNS....
We have a new Library management system and the url you have to type in is http://servername:81 which to most people in the school it doesn't mean much. I would like for instants for people to simply type in 'eclipse' in there browser and be automatically redirected to the right place. Do I do this with a CNAME alias within DNS??
You can do, but that won't take care of the port issue. You'll need to set up a host header as well, then set it to port 80.
You can certainly create a CName (DNS Alias) for the server name to something more meaningful, but users would still have to type http://eclipse:81
Assuming you're using an MS IIS Web server, what you'd also need to do is configure the IIS server to look out for your new preferred name and forward the request to the appropriate hosted site. You can do this with a feature called "host headers". Have a search for that relating to your version of IIS and you should find what you need.
or just a create a favourite in the browser via group policy