When working with Hyper-V Server R2 in an Active Directory environment, administrators often encounter the "RPC server is unavailable" error when attempting to access Disk Management through MMC. This typically occurs despite both machines being domain-joined and having proper network connectivity.

The root causes usually fall into these categories:

• Windows Firewall blocking RPC ports (TCP 135, 49152-65535)
• Disabled Remote Volume Management service
• Incorrect DCOM permissions
• Network profile set to "Public"
• DNS resolution problems between nodes

First, confirm basic RPC functionality with these PowerShell commands:

Test-NetConnection -ComputerName HyperVServer -Port 135
Get-Service -ComputerName HyperVServer -Name VDS | Select-Object Status,Name

Create a firewall rule group policy or run these commands on the Hyper-V server:

New-NetFirewallRule -DisplayName "Allow RPC Endpoint Mapper" -Direction Inbound -Protocol TCP -LocalPort 135 -Action Allow
New-NetFirewallRule -DisplayName "Allow RPC Dynamic Ports" -Direction Inbound -Protocol TCP -LocalPort 49152-65535 -Action Allow
Set-NetConnectionProfile -InterfaceAlias "Ethernet" -NetworkCategory Private

Ensure these services are running and set to Automatic:

Get-Service -Name VDS,RPCLocator,DcomLaunch | Set-Service -StartupType Automatic -PassThru | Start-Service

For advanced DCOM permissions, use dcomcnfg.exe to:

1. Navigate to Component Services > Computers > My Computer
2. Right-click > Properties > COM Security tab
3. Adjust Launch and Activation permissions for the connecting user

If the issue persists, consider these alternatives:

# Using PowerShell for disk management instead
Get-Disk -CimSession HyperVServer | Initialize-Disk -PartitionStyle GPT
Get-Partition -CimSession HyperVServer | Format-Volume -FileSystem NTFS -Force

For remote WMI access (another fallback option):

winrm quickconfig -force
Set-NetFirewallRule -Name WINRM-HTTP-In-TCP -RemoteAddress Any

When all else fails, reset the networking components:

netsh int ip reset
netsh winsock reset
Restart-Computer -Force

When attempting to connect to the Disk Management MMC console on Hyper-V Server R2, many administrators encounter the frustrating "RPC server is unavailable" error. This typically occurs even when:

• Both servers are in the same Active Directory domain
• MMC console access is properly enabled on the Hyper-V host
• Basic network connectivity exists between machines

From my troubleshooting experience, this error most frequently appears in these situations:

1. After recent Windows Updates on either the management workstation or Hyper-V host
2. When connecting from a Windows 10/11 workstation to Server 2008 R2
3. In environments with strict firewall rules between subnets
4. When using non-domain admin credentials with insufficient privileges

Before diving deep into RPC troubleshooting, let's check some fundamentals:

# PowerShell test for basic RPC connectivity
Test-NetConnection -ComputerName HV-HOST -Port 135

# Verify WMI connectivity
Test-WSMan -ComputerName HV-HOST

# Check if Remote Volume Management service is running
Get-Service -ComputerName HV-HOST -Name vds

These services must be running on the Hyper-V host:

# Critical services for Disk Management MMC
$requiredServices = @(
    "Remote Procedure Call (RPC)",
    "DCOM Server Process Launcher",
    "RPC Endpoint Mapper",
    "Virtual Disk Service",
    "Windows Management Instrumentation"
)

foreach ($service in $requiredServices) {
    $status = Get-Service -Name $service
    Write-Output "$service : $($status.Status)"
}

Proper firewall rules are crucial for RPC communication. Create these rules if missing:

# PowerShell to enable required firewall rules
$rules = @{
    "Remote Volume Management" = @("TCP", "445")
    "Remote Event Log Management" = @("TCP", "139,445")
    "Windows Management Instrumentation (WMI)" = @("TCP", "135")
}

foreach ($rule in $rules.GetEnumerator()) {
    New-NetFirewallRule -DisplayName $rule.Key 
        -Direction Inbound 
        -Protocol $rule.Value[0] 
        -LocalPort $rule.Value[1] 
        -Action Allow
}

For older Hyper-V hosts, these registry changes might help:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Ole]
"EnableDCOM"="Y"
"LegacyAuthenticationLevel"=dword:00000002

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa]
"restrictanonymoussam"=dword:00000000

When traditional MMC fails, consider these alternatives:

# PowerShell Disk Management alternative
Get-Disk -CimSession (New-CimSession -ComputerName HV-HOST)

# Using DiskPart remotely
$scriptBlock = {
    diskpart /s C:\scripts\diskconfig.txt
}
Invoke-Command -ComputerName HV-HOST -ScriptBlock $scriptBlock

• Verified all required services are running
• Confirmed firewall isn't blocking RPC traffic
• Checked DCOM permissions and settings
• Validated credentials have proper privileges
• Tried alternative management methods