I suggest to use Host Headers (domain names) assigned to the IPs in IIS web site configuration instead of port numbers.

If you want to use DNN multiportal feature, you may assign all host headers to the same web sites and assign portal those as portal aliases to the appropriate web sites - and DNN will open the correct web site for you.

 no, if you need to access it from multiple machines inside your LAN, you may add the domain address to your DNS, if you just need to use it locally you may add the address to /windows/system32/drivers/etc/host file as alias (just add the name after localhost separated by spaces). I use this to install multiple DNN versions on my vista machine to address it using http://dnn493 or http://dnn501b3

If you are using WindowsXP, i suggest to use free IIS admin pro from www.jetstat.com