Synology Active Directory ADS join domain fix (suddenly nas lost connection to domain)

gistfile1.ps1

# Your NAS Synology device suddenly lost connection to your Windows Domain Controller, and or intermittent AD connectivity issues.
# Symptoms include but not limited to: 
# - Failing to rejoin after removing the account on the Domain. 
# - Failing to rejoin without any changes
# - Join attempt results in = "Failed to join the Windows domain. Please check your domain and firewall settings and try again"
# - Synology is joined, but attempting to connect from domain clients results in "There are no logon servers available to service the logon request"
# - This problem happens intermittently, sometimes rebooting the Synology device allows you to rejoin (Not a solution). 
# - Sometimes rebooting both Synology device and Domain Controller allows you to rejoin (Not a solution).

# 1st.) *OPTIONAL* Remove the AD Synology device from Avtice Directory Users/Computers.
#       Step could be required if your Synology system is currently in a disconnected state.
#       ie: Inaccessible from Domain systems, and or "no login servers available".
#       Always try Step 2 first, you have nothing to lose. Permissions for Domain Users/Groups, entered
#       on your Synology system, for shared folders do not get removed when the Synology Computer object
#       is deleted from the Domain's Active Directory Users/Computers.

# 2nd.) *THE FIX*) Enable SMB1 Protocol - Try the following commands on your Domain Controller:
#   Use the appropriate commands for the terminal/console/shell you are using.
#   Goal: Enable SMB1 and restart LanmanWorkstation and LanmanServer SMB Windows services

# powershell v4 (ws2012+)
Set-SmbServerConfiguration –EnableSMB1Protocol $true
# powershell v2 (ws2k8)
Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters" SMB1 -Type DWORD -Value 1 -Force
# cmd (cmd/run)
reg.exe ADD 'HKLM\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters' /v SMB1 /t REG_DWORD /d 0x1 /f

# restart SMB services (Powershell)
Restart-Service LanmanWorkstation -Force; Restart-Service LanmanServer -Force
# restart SMB services (cmd)
net stop LanmanWorkstation & net start LanmanWorkstation
net stop LanmanServer & net start LanmanServer
# sc cmd method
sc stop LanmanWorkstation & sc start LanmanWorkstation
sc stop LanmanServer & sc start LanmanServer

# 3rd.) Enjoy the problem never happening again. You might also want to setup a WINS server, since Synology boxes seem to function
#      much better with one available to them.

# Info: Why would SMB1 all of a sudden be relevant to a previously joined device with it disabled? No Clue.
# Since I don’t use SMB for anything on the related Domain Controller, I now schedule a task to restart SMB services
# once a day. If the problem persists you may want to evaluate your Domain's Network Permissions (Securty Settings)
# for NTLM authentication. I can see this being an issue for certain environments. Might want to look into adding an
# server exception for your NAS. Granted i have not tested a Synology with zero NTLM (no NTLMv2 only Krb). I am also not sure
# what data is passed from NAS to DC in regards to SMB1. Somepoint i will setup a lab and capture data with SMB1 enabled/disabled,
# and the activity of the synology system in a dissconnected domain state.