I won't bother explaining the various groups of available IPs, that has already been covered in other posts. However, with regard to your question on submasks, there are a few variables involved. If you want to keep your network as open to change as possible, you could simply leave the subnet mask at 255.0.0.0 and use the 10.xxx.xxx.xxx range. Just keep adding addresses as needed. The problem that can arise is when you want to treat nodes differently, such as limiting internet access via firewall and grouping nodes such as servers / notebooks. I am a big advocate of splitting your IPs into groups. This means that you can keep track of PCs at an IP level more easily and also set a standard system that can be kept for a long period. Here's an example: subnet mask 255.255.0.0 network 1 = 10.10.0.0 network 2 = 10.20.0.0 network 3 = 10.30.0.0 laptops = 10.xx.50.xxx (dhcp range) servers = 10.xx.25.xxx desktops = 10.xx.0.xxx The above example has a series of gateway's between the networks. Normally found at 10.xx.0.1. This setup allows me to quickly split our PCs into various groups depenting on the configuration. It also leaves room for identifying larger groups by state / city. However, there is enough room left by my subnet mask, that I can change most of my PCs without needing to play with the mask in the future. ---- Michael Pemberton mpember at phreaker.net -- Original Message -- From: "Chris W. Parker" <cparker at swatgear.com> To: thelist at lists.evolt.org Send: 2002-11-01 Subject: internal ip schemes (was RE: [thelist] IIS5: subdomains, how to configure) ... when would i need to change the subnet mask, if ever?