Connectivity problems after server in-place upgrade (suspected DHCP issue)

princeofpersia

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Hello folks. Earlier this week I performed an in-place upgrade of an office server (single processor, domain controller) from Windows Server 2008 R2 Standard to 2012 R2 Standard. It is being hosted on a Dell PET410, Intel Xeon E5620 2.4GHz, 8GB RAM.

I ask for your kind understanding - unlike some other issues which I've brought up in this forum, I have minimal experience in working with servers. This upgrade was my first time learning everything from scratch. Therefore please let me know of any necessary details that I've not provided.

I troubleshooted and carried out all the necessary updates/repairs pre-upgrade, and the upgrade itself went smoothly. However, post-upgrade some PCs were not able to connect to EITHER the server OR the Internet OR both. Some PCs had zero connectivity issues. The PCs affected (and how they were affected) were seemingly random, and since the entire network was done by a contractor in 2010, there was nothing to refer to in terms of how things were set up. I can only assume there was a lot of patchwork as the number of workstations increased over the years.

By sheer trial and error (basically comparing settings with unaffected PCs), I managed to resolve the issue as follows:
1. Change IPv4 settings from DHCP/Automatic to Static/Manual
- Use DNS 1.1.1.1 and 1.0.0.1 for devices connected via ethernet
- Use DNS 8.8.8.8 and 8.8.4.4 for devices connected via wifi
2. Add "server.local" as DNS suffix (previously empty)

I am posting this here with the aim of finding out
- exactly what went wrong
- why my solution works and whether it will result in any future problems
- the "correct" solution

Thank you!
 
Windows Version
Windows Server 2012 R2 Standard

My Computer

System One

  • Operating System
    Windows 7 Professional

johngalt

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Knowing a bit more about the network topology would probably be the first step - understanding what devices reside inline between the workstations and the server(s) (if any at all do, in fact, lie in between) will be necessary before any sort of definitive answer can be given, because those devices that are inline may (or may not) have contributed to the issue. So, switches (or, if the contractor was cheap, hubs *shudder*) may play a part in the connectivity (or lack thereof).
 

My Computer

System One

  • Operating System
    Windows 10 Pro X64
    Computer type
    PC/Desktop
    Manufacturer/Model
    The Beast Model A (homebrew)
    CPU
    AMD Ryzen 9 3950X
    Motherboard
    MSI MEG X570 GODLIKE
    Memory
    4 * Corsair Vengeance 32 GB 3600 MHz
    Graphics Card(s)
    eVGA GeForce GTX 970 SSC ACX 2.0 (04G-P4-3979-KB)
    Sound Card
    Realtek® ALC1220 Codec
    Monitor(s) Displays
    2 * Lenovo LT2323pwA Widescreeen @ 1920*1080
    Hard Drives
    3x Sabrent Rocket PCIe Gen4 NVMe M.2 1 TB SSD (SB-ROCKET-NVMe4-1TB)
    SanDisk Ultra SDSSDHII-960G-G25 960 GB SATA III SSD
    2 * Seagate Barracuda 7200.12 ST31000528AS 1TB 7200 RPM --> RAID1
    PSU
    PC Power & Cooling’s Silencer Series 1050 Watt, 80 Plus Platinum
    Case
    Fractal Design Define 7 XL Dark ATX Full Tower Case
    Cooling
    NZXT KRAKEN Z73 73.11 CFM Liquid CPU Cooler + Air (3 * 140mm fans from case)
    Keyboard
    SteelSeries Apex Pro Wired Gaming Keyboard
    Mouse
    Logitech MX Master 3 Wireless Laser Mouse(shared)
    Internet Speed
    AT&T Lightspeed Gigabit duplex
    Browser
    Nightly|Chrome|Canary|Edge+ (Chromium) (in all 4 flavors)
    Antivirus
    Windows Defender + MB 4
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