When attempting to establish Remote Desktop Protocol (RDP) connections from Windows 7 workstations to newly deployed Windows Server 2008 R2 systems using hostnames, administrators encounter:

The connection cannot be completed because the remote computer that was reached 
is not the one you specified. This could be caused by an outdated entry in the 
DNS cache. Try using the IP address of the computer instead of the name.

The issue demonstrates these characteristics:

• Exclusive to Windows 7 → Windows Server 2008 R2/R1 connections
• Works when using IP addresses instead of hostnames
• Non-R2 servers and non-Win7 clients function normally

The problem stems from a mismatch in how Windows 7 and Server 2008 handle DNS resolution during RDP handshake:

// Pseudo-code of the resolution process
if (client.OS == Windows7 && server.OS == Server2008R2) {
    verifyHostname(connectionRequest) {
        // Bug occurs in this verification layer
        return incorrectHostnameError; 
    }
}

Solution 1: DNS Cache Flush (Temporary Fix)

Execute on Windows 7 client:

ipconfig /flushdns
nbtstat -R

Solution 2: Hosts File Entry (Permanent Fix)

Modify %SystemRoot%\System32\drivers\etc\hosts:

# RDP Fix for Server2008R2
192.168.1.100    server01.company.local

Solution 3: Registry Modification

Create this registry key on Windows 7 clients:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services]
"DisableUDPPort"=dword:00000001

For network administrators needing deeper diagnosis:

# PowerShell DNS verification
Test-NetConnection -ComputerName server01 -Port 3389
Resolve-DnsName server01.company.local | Format-List

• Ensure consistent DNS configuration across all domain controllers
• Verify reverse DNS (PTR) records exist for all servers
• Consider implementing DNSSEC for enhanced validation

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When establishing RDP connections between Windows 7 clients and Windows Server 2008 R2 (or even non-R2) systems, you might encounter this cryptic error:

The connection cannot be completed because 
the remote computer that was reached is not 
the one you specified. This could be caused 
by an outdated entry in the DNS cache. Try 
using the IP address of the computer instead 
of the name.

The issue exhibits these specific characteristics:

• Only occurs between Windows 7 clients and Server 2008/R2 targets
• Works fine when using IP addresses instead of hostnames
• No issues when connecting from non-Win7 clients to 2008/R2
• No problems when Win7 connects to non-2008/R2 servers

The core issue stems from TLS/SSL certificate validation during RDP handshake:

1. Windows Server 2008/R2 presents its certificate during connection
2. Windows 7 performs strict hostname verification against the cert's SAN
3. DNS caching issues cause mismatched hostname resolution

Method 1: Flush DNS Cache

Run this command on the client machine:

ipconfig /flushdns

Method 2: Use IP Address Connection

Create a new RDP shortcut with:

mstsc /v:192.168.1.100

Option 1: Update DNS Records

Ensure your DNS server has:

server01.example.com.   IN  A   192.168.1.100

Option 2: Certificate Fix

On the server, run this PowerShell to check cert binding:

Get-ChildItem -Path Cert:\LocalMachine\My | 
Where-Object {$_.Subject -match "server01"} | 
Select-Object Subject, Thumbprint

For enterprise environments, modify this registry key on Win7 clients:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System\CredSSP\Parameters]
"AllowEncryptionOracle"=dword:00000002

Save as rdp_fix.reg and merge.

After applying fixes, verify with:

nslookup server01.example.com
ping server01.example.com
Test-NetConnection -ComputerName server01 -Port 3389