I administer the network in my (very small, ~110 students) school. We have a Windows Server 2008 R2 Standard server, and we use Windows 7 Professional. We have ~10 workstations and 5 laptops, the latter of which connect sometimes over Ethernet, and sometimes over Wi-Fi. I've noticed that this creates duplicate DHCP leases, and then only one of those can get registered in DNS -- the second simply fails. Is there any way to fix this, so that when I, for example, ping laptop-1, it'll get to the laptop no matter which interface is currently in use?
This post reiterates some of what we've already discussed in the comments under your original post for the benefit of others, but goes further to (hopefully) address your issue.
A DHCP server leases IP addresses to clients based on the clients reported MAC address. So, if a computer has two network interfaces, LAN & WLAN (Wireless LAN), each with its own MAC address, you can end up with two DHCP leases. Both leases will report the same computer name, but if you examine the MAC address (or Unique ID), you’ll note they are actually different records.
In short, the answer to your question is yes – a laptop’s hostname can be associated with both of its interfaces? However, there are a few caveats.
Once the client receives a leased IP address from DHCP, one of several things can happen in regard to DNS registration:
If the DNS server is configured to allow only secure dynamic updates, the first system to update the record becomes the owner and all other attempts to access the DNS record will result in access violations. For example, if the client registers its DNS record first, the DHCP service might encounter something like the errors Micha has described.
When the DHCP service registers a connection on behalf of a client, it will register the most recently leased or renewed IP address using the name supplied by the client. Consider the following:
Unless you have some compelling reason why the DHCP server should be registering IP addresses on behalf of its clients, you should leave DNS registrations to the individual clients. Unlike the DHCP server, the client will register multiple DNS entries – one for each network adapter with an IP address. Consider the following:
To summarize, this is what you want:
How to configure DNS for secure dynamic updates:
How to configure DHCP to NOT update DNS for all clients:
Configure windows to refresh dynamic DNS registrations at fixed intervals:
Apply the following group policy setting to all of your computers (or just the laptops):
Note: If you need a shorter refresh interval you could try creating a scheduled task using group policy to run “ipconfig /registerdns”. The command requires elevated privileges, so this option might introduce unwanted security risks.
Hope this helps!