DHCP

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Apple Mac computers lose connectivity to on-premise Exchange server

Every day we experienced many of our Macs losing their connection to the mail server which happened to be a Microsoft SBS 2008 server. For many months the solution was to connect to the public wireless connection that was OK for the users but it was just a workaround. Connectivity would be sporadic and having the Macs connected to the LAN over the wire and to the public wireless connection wasn’t a good long term solution.

After much troubleshooting I figured out that the configuration of their DNS and DHCP servers was incorrect. Research and testing revealed that Macs use Autodiscover to connect to the Exchange server. Internal DNS didn’t have the autodiscover records required by internal Exchange clients. And it didn’t matter what client – Entourage, Apple Mail, Outlook for Mac – they all lost connectivity quite often and a random times. Once was resolved but adding the proper records there was one other problem.

DHCP was configured to assigned the SBS server AND and external DNS server for DNS. Once that was rectified by setting DHCP to assign just the SBS server as the DNS server and running DNS Bench to determine the fastest DNS servers for the office and setting them as the forwarders, the Macs maintained stable connectivity to the Exchange server. Finally!

Why was this the case? The Macs need Autodiscover records to be set up correctly in DNS. That’s why connecting over public wireless connection worked. The external DNS servers had Autodiscover records set up correctly for external clients. Luckily this worked for their environment as a band-aid. When the internal one wasn’t configured correctly the Macs could never connect to the Exchange server using the internal DNS server to resolve hostnames.

Why was it sporadic? I chalk it up to the sometimes slow DNS name resolution of the SBS server. If it didn’t respond quick enough, it would force the Macs to use the external DNS server for name resolution and would work, but if the SBS server did respond in time, they would lose connectivity.

So fixing both was necessary – DHCP to only assign the SBS server as the internal DNS server and for DNS to be configured with the correct Autodiscover records.

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Blank Desktop, No Mapped Drives

Had a weird issue pop up recently. The background is this. The client had a new Windows 2012 server installed running as a domain controller, DHCP, DNS, and file server. Some new switches were installed.

The issue I came in to help with was that people were not able to connect to the network for some reason. These were people who just came back from a long period of time and logged in but were not getting connectivity to the network drives or printers. We thought that the solution was to put them into another port on the switches which did work for some people but for some reason it didn’t work that day.

As I was trying to figure out this problem, another issue arose. I rebooted someone’s PC who was having network connectivity problems and all I got was a blank desktop with a cursor for the mouse. Even in safe mode, I got the same symptom. Checking IPCONFIG I got the 169.x.x.x address. You know what that means, it wasn’t getting an IP assignment from the DHCP server.

Another tidbit of information – this network didn’t have folder redirection or roaming profiles so it wasn’t either of those that was causing issues. After some trial and error, I was able find a Band-Aid while we worked towards a solution. The temporary fix was to disconnect the LAN cable, log in, then connect back up. After that, people were able to use their PCs. But the issue still remained without employing the Band-Aid fix. Why are they getting blank screens with a mouse pointer and nothing else?

We don’t know exactly what fixed it but we did a few things and either one or a combination of the things we did apparently fixed the problem. Rebooted all the switches. And I found that the DHCP wizard was complaining about something not being completed. I ran through the wizard to finish it all up. I don’t remember exactly what it was but some final steps needed to be completed. I believe there are some accounts/groups that needed some DHCP service permissions that it found wasn’t done. Rebooted the new 2012 server.

After doing those, the network authentications problems, network connectivity issues, and blank screens all disappeared. My personal feeling is that the DHCP wizard needed to finish up the permissions. The reason I think that is because of the fact that client PCs were not getting IP assignments. In any case, the problem was fixed and everyone was back to work within a few hours.

Hope this helps someone.