From Dynamic IP Addresses and Back

By Ronald Pacchiano | Posted October 07, 2005

I serve as a one-man IT department for my family business, and I don't have the time to learn (much less understand) all of the intricacies of networking. In spite of this deficiency, though, I've managed to keep everyone connected, working and secured for about 10 years now. Our little five-person office network uses a cable broadband connection for our Internet communication. We use both wired and wireless PCs around the office and have DHCP enabled on the router to handle IP address assignments.

I've just purchased a networked BizHub and the installation techs say it will require a static IP address. Since we currently use DHCP for our IP address assignments, I'm wondering if it's even possible to use both dynamic and static addresses at the same time. If not, will we need to switch everyone over to a static IP? Lastly, how does one determine the appropriate static IP(s) to use in these cases?

Don't stress over this -- you can use both static and dynamic IP addresses on the same network. The reason the BizHub requires a static IP address is because, unlike your client PCs, everyone in your office will need to access the BizHub. A static IP address ensures that your client PCs will always locate the unit. On the other hand, if you had configured the hub to use a dynamic IP address, then the address would change from time-to-time, causing the client PCs to occasionally lose communication with it. To correct that situation, you'd have to update the driver with the BizHub's new IP address every time it changed. Depending on the number of people you have and the frequency of the IP changes, this could be more than a little problematic.

The only client-side task you need to take care of on a system or device that needs a static IP address is modify its TCP/IP configuration with the proper gateway, subnet mask and DNS addresses. Once you save the configuration, the device should be online.

Selecting the IP address is pretty simple. Essentially, all you do is give the BizHub any address outside of your DHCP scope. For example, let say your DHCP scope was 192.168.0.50 through 192.168.0.100. This means that you have 50 IP addresses available to use with DHCP. So any address that falls between these two numbers (e.g., 192.168.0.72 or 192.168.0.90) will be automatically assigned to any client with DHCP enabled. You can use any of the IP addresses outside of this range as a static IP address.

Usually, I find it easier to manage IP addresses if I divide them into sections. For example, I would reserve 192.168.0.1 through 192.168.0.30 for use with network routers and servers. Then I would use the address range 192.168.0.31 through 192.168.0.49 for network peripherals such as your BizHub, scanners, copiers or printers. Finally, I'd use the remaining addresses (in this case 192.168.0.50-192.168.0.100) for the DHCP scope. This way I always know what IP addresses are available.

Another method is to use DHCP to assign the BizHub an IP address, but you can configure the DHCP scope to always give the BizHub the same IP address based on its MAC address. This ensures that the BizHub will always be assigned the same dynamic address, giving you all the benefits of a static address, without you having to make any changes to your DHCP scope.

The nice thing about this is that you won't need to configure any of the TCP/IP settings manually. Most DHCP servers will support this feature and your routers documentation should be able to walk you through the setup.

Either method works, so choose whichever one is more comfortable for you.

I have a Dell laptop computer running Windows XP, and it's equipped with a Linksys wireless network adapter that I use to connect to our school's domain. When I attempt to log on to the school's network, I receive this error message: "duplicate name exists on the network." I then clear the error and continue logging on. Once connected, I can browse the Internet. However, when I go to My Network places and drill down to the domain name, I can't see any of the other computers on the network. Going under the assumption that this is a duplicate name on the network, I attempted to change the name of the computer, but was told I didn't have the rights to do so. I have checked the TPC/IP configurations of some of the other Dell computers in our lab, and they appear to be similar. Do you have any suggestions about how I should go about resolving this? Any ideas would be appreciated. Thanks.

When you have a duplicate name on the network, the system prevents you from gaining access to the domain and, subsequently, from browsing Network Neighborhood. I think you were definitely on the right track when you tried changing the computer name. This was a common error I used to come across when rolling out new systems -- particularly ones that had been setup using a Ghost image. Considering that you didn't have the rights to change the computer when you were logged in with your account, I'm wondering if this is a school laptop that was recently imaged. If that's the case, you'll need to get the school's IT department to assist in correcting this problem.

In any case, the way to get around this is simple. You need to log onto your laptop using the local network administrator's account. Once logged in, change the name of the computer. Once you reboot the system you should be able to gain access to the domain. If not, you might need to login locally again and remove the laptop from the domain by making it a member of a workgroup. At this point it will prompt you to restart the system. Once restarted, log in locally again and rejoin the domain. You're going to need access to an account that has rights to join the school domain. If that's not you, as I suspect, then you'll need to coordinate your efforts with the schools IT department. Once that's been accomplished, restart your system. You should now be able to logon with your regular network account. I hope this helps

Adapted from PracticallyNetworked.com, part of the EarthWeb.com Network.

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