To establish a VPN connection between Windows 7 and Ubuntu Linux, you'll need:

1. Ubuntu server (18.04 LTS or later recommended)
2. Windows 7 Professional/Enterprise/Ultimate (Home edition lacks VPN client)
3. Root access on both machines
4. Static IP or DDNS for your Ubuntu server

Windows 7's native VPN client supports these protocols:

1. PPTP (Point-to-Point Tunneling Protocol)
2. L2TP/IPsec (Layer 2 Tunneling Protocol)
3. SSTP (Secure Socket Tunneling Protocol)

For quick deployment, PPTP is the simplest option:

sudo apt-get update
sudo apt-get install pptpd -y

# Configure PPTP
sudo nano /etc/pptpd.conf
# Add these lines:
localip 192.168.0.1
remoteip 192.168.0.234-238

Create VPN credentials in /etc/ppp/chap-secrets:

# Format: username pptpd password *
vpnuser pptpd MySecurePassword123 *

Enable IP forwarding and configure NAT:

sudo nano /etc/sysctl.conf
# Uncomment or add:
net.ipv4.ip_forward=1

sudo sysctl -p
sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
sudo iptables-save > /etc/iptables.rules

1. Open Network and Sharing Center
2. Click "Set up a new connection"
3. Select "Connect to a workplace"
4. Choose "Use my Internet connection (VPN)"
5. Enter server IP/DNS and connection name
6. Select "PPTP VPN" as the VPN type

If connection fails, check:

# Ubuntu server logs:
tail -f /var/log/syslog

# Windows event viewer:
Event Viewer > Windows Logs > System

PPTP has known vulnerabilities. For better security, consider:

sudo apt-get install openswan xl2tpd
# Configure L2TP/IPsec with pre-shared keys

For maximum security, use OpenVPN (requires client software on Windows):

sudo apt-get install openvpn easy-rsa
cd /usr/share/easy-rsa/
source vars
./clean-all
./build-ca
./build-key-server server
./build-key client1

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Yes, you can absolutely set up a VPN server on Ubuntu that's compatible with Windows 7's built-in VPN client. The most straightforward protocols that work with Windows 7's native VPN connection wizard are:

• PPTP (Point-to-Point Tunneling Protocol)
• L2TP/IPsec (Layer 2 Tunneling Protocol with IPsec)

For quick setup, PPTP is the easiest option though less secure than modern alternatives. Install PoPToP server:

sudo apt-get update
sudo apt-get install pptpd

Edit the configuration file:

sudo nano /etc/pptpd.conf

Add these lines:

localip 192.168.0.1
remoteip 192.168.0.234-238,192.168.0.245

Set up user credentials in /etc/ppp/chap-secrets:

# Format: username pptpd password *
vpnuser1 pptpd MySecurePass123 *
vpnuser2 pptpd AnotherSecurePass456 *

On Windows 7:

1. Open Network and Sharing Center
2. Click "Set up a new connection or network"
3. Select "Connect to a workplace"
4. Choose "Use my Internet connection (VPN)"
5. Enter server IP and connection name
6. Select "PPTP VPN" as the VPN type

For better security, use L2TP/IPsec with xl2tpd and strongSwan:

sudo apt-get install xl2tpd strongswan

Configure /etc/ipsec.conf:

conn %default
    ikelifetime=60m
    keylife=20m
    rekeymargin=3m
    keyingtries=1
    keyexchange=ikev1
    authby=secret
    ike=aes256-sha1-modp1024!
    esp=aes256-sha1-modp1024!

If connection fails:

• Check firewall rules (open ports 1701, 500, 4500 for L2TP)
• Verify NAT traversal is enabled if behind a router
• Ensure proper routing tables on the server