This guide walks you through deploying a PPTP VPN to provide remote access to an on-premise ERP system. It focuses on practical configuration steps, useful command examples, routing and firewall considerations, authentication options, and operational security measures. While PPTP is easy to deploy and widely supported, it has known security limitations; this article shows how to harden a PPTP deployment for pragmatic use cases such as temporary remote access, legacy client support, or low-risk internal networks.

Why choose PPTP (and when not to)

PPTP (Point-to-Point Tunneling Protocol) remains popular because of its simplicity and wide client support (Windows, macOS, Linux, many embedded devices). It encapsulates PPP frames into GRE and uses TCP for control. Typical advantages:

  • Fast to deploy and client-ready on most platforms.
  • Minimal configuration for end users—often built into OS VPN clients.
  • Low CPU overhead compared with some IPsec/SSL solutions.

However, PPTP has well-documented security weaknesses (notably MS-CHAPv2 vulnerabilities and weaker encryption). For production systems with strict compliance or high-risk data, prefer IPsec or OpenVPN/WireGuard. If you must run PPTP, apply mitigations described below and limit usage to trusted endpoints, dedicated IPs, and short time windows.

High-level architecture for ERP access

A typical topology for remote ERP access via PPTP includes:

  • A public-facing VPN server with a static public IP (or dedicated IP delivered by your provider).
  • The ERP application server(s) on a protected internal subnet.
  • Firewall/NAT translating VPN client traffic into the internal network and enforcing ACLs.
  • Optional RADIUS/LDAP/AD for centralized authentication.
  • Logging and monitoring (syslog, fail2ban, IDS).

IP planning and routing

Choose a dedicated VPN address pool that does not overlap with other networks (e.g., 10.254.100.0/24). Configure the VPN server to assign addresses from that pool, then set static routes on the ERP servers or on the network gateway so ERP traffic returns via the VPN server. Example:

  • Public IP: 198.51.100.10 (VPN server WAN)
  • VPN subnet: 10.254.100.0/24
  • ERP server: 192.168.10.20 on internal LAN

Ensure IP forwarding is enabled on the VPN host and that NAT or routing is configured to reach the ERP subnet.

Example: Linux (Ubuntu/Debian) pptpd deployment

Below are concrete steps and config fragments to set up pptpd on a Debian/Ubuntu host. Adjust package manager commands and file paths for other distros.

Install and enable packet forwarding

Install pptpd:

sudo apt update && sudo apt install pptpd

Enable IPv4 forwarding:

sudo sysctl -w net.ipv4.ip_forward=1

To make it persistent:

echo "net.ipv4.ip_forward=1" | sudo tee -a /etc/sysctl.conf

Configure PPTP server

Edit /etc/pptpd.conf and add localip and remoteip range:

localip 192.168.200.1
remoteip 10.254.100.10-10.254.100.100

These assign the server-side address and the client pool. Then configure PPP options in /etc/ppp/options.pptpd:

ms-dns 192.168.10.1 # internal DNS that resolves ERP host
name pptpd
lock
nobsdcomp
nodeflate
mtu 1400

Note: disable compression options to avoid certain attacks and ensure stability.

Authentication — chap-secrets and RADIUS

For local accounts use /etc/ppp/chap-secrets with a simple format:

# client server secret IP addresses
erpuser pptpd VeryStrongP@ss1 *

For centralized auth, configure /etc/pptpd.conf or pppd to use RADIUS. Add a RADIUS server line (example for FreeRADIUS):

plugin radius.so

Then configure /etc/freeradius/clients.conf and the shared secret. Centralized auth allows user lockouts, password policies, and MFA orchestration (see below).

Firewall/NAT with iptables

MASQUERADE outbound traffic so VPN clients can reach internal subnets when necessary. Example iptables (replace if using nftables or firewalld):

sudo iptables -t nat -A POSTROUTING -s 10.254.100.0/24 -o eth1 -j MASQUERADE

Allow GRE and PPTP control:

sudo iptables -A INPUT -p tcp --dport 1723 -m conntrack --ctstate NEW -j ACCEPT
sudo iptables -A INPUT -p gre -j ACCEPT

Restrict access to the public VPN port by source IP (if feasible) and add rules to allow only the ERP application ports from VPN pool to ERP subnet.

Windows Server (RRAS) basic steps

If you prefer Windows Server RRAS:

  • Install Remote Access role and choose VPN only (DirectAccess not required).
  • Configure RRAS for PPTP with static IP pool or DHCP allocation.
  • Bind RRAS to the public NIC and set the public IP as the listener.
  • Integrate with Active Directory for user authentication and group policy control.
  • Enable strong password policies and consider NPS (Network Policy Server) with RADIUS for advanced rules.

Client configuration

Windows built-in client:

  • Settings → Network & Internet → VPN → Add a VPN connection
  • VPN provider: Windows (built-in); Connection name: ERP-PPTP; Server name: 198.51.100.10; VPN type: Point to Point Tunneling Protocol (PPTP); Type of sign-in info: Username and password

macOS: Use Network Preferences → Add VPN → PPTP (requires third-party software on newer macOS versions because Apple deprecated PPTP in macOS Sierra and later).

Linux: Use NetworkManager-pptp or command-line pppd/pptp-linux client. Example command:

sudo apt install pptp-linux
sudo pptpsetup --create erpvpn --server 198.51.100.10 --username erpuser --password VeryStrongP@ss1 --encrypt

Security hardening and mitigations

Because PPTP and MS-CHAPv2 have weaknesses, apply the following mitigations to reduce risk:

  • Use strong, unique passwords and enforce password rotation. MS-CHAPv2 is vulnerable to offline attacks; longer, complex passwords increase attack cost.
  • Limit access to a fixed set of public IPs (source filtering) if users have predictable endpoints or a dedicated IP from your provider.
  • Use RADIUS with account lockout and monitoring. Centralized logging helps detect brute-force attempts.
  • Enable fail2ban or equivalent to block repeated authentication failures and throttle connections.
  • Restrict VPN user permissions: only allow access to ERP subnets and ports (e.g., TCP 80/443, 3306, etc.). Don’t grant full LAN access unless required.
  • Turn off PPTP encryption negotiation fallbacks and force MPPE 128-bit where supported.
  • Apply OS and packages security updates promptly on VPN hosts.
  • Consider layering with MFA: while PPTP itself doesn’t carry native MFA, you can integrate RADIUS servers (e.g., FreeRADIUS) that add OTPs or push-based MFA before authorizing PPP sessions.

Hardening PPP options

In /etc/ppp/options.pptpd, ensure options include:

require-mschap-v2
refuse-chap
refuse-eap
noauth

Forcing MS-CHAPv2 and refusing older/less secure authentication methods reduces the attack surface. Still, MS-CHAPv2 should be considered weak relative to modern VPN protocols.

Monitoring, testing, and troubleshooting

Key diagnostics:

  • Check PPP logs: /var/log/syslog or /var/log/messages for pppd/pptpd negotiation details.
  • Use tcpdump to capture GRE traffic and PPP negotiation: sudo tcpdump -i eth0 -n host 198.51.100.10 or proto gre
  • Verify routing: from a VPN client, traceroute to ERP host to ensure packets traverse expected route.
  • Test DNS resolution against the ERP DNS server from the VPN client to ensure proper name lookups.
  • Monitor authentication failures and look for patterns that indicate brute force attacks; tune fail2ban or firewall accordingly.

Common issues and fixes:

  • Clients can connect but cannot reach ERP: check IP forwarding, iptables MASQUERADE, and return routes on the ERP server/gateway.
  • GRE blocked: ensure middleboxes allow protocol 47 and not only TCP/UDP ports.
  • Authentication failures: validate chap-secrets or RADIUS shared secret, and ensure server time sync for time-based MFA.

Operational recommendations

For production-grade remote ERP access, treat PPTP as a pragmatic, temporary or fallback solution rather than the long-term default. Recommended operational measures:

  • Provide a dedicated public IP for the VPN endpoint and restrict IP exposure with upstream ACLs if supported by the provider.
  • Maintain an audit log retention policy and export logs to centralized SIEM for correlation with ERP access records.
  • Implement regular reviews of VPN user accounts, removing inactive user entries and rotating shared secrets.
  • Test disaster recovery: make sure VPN access is included in your runbooks for ERP failover scenarios.
  • Plan migration to a stronger VPN solution (IPsec, OpenVPN, or WireGuard) and document client migration steps.

When to migrate off PPTP

If your ERP handles sensitive customer, financial, or regulated data, plan to migrate to an encrypted, authenticated VPN that uses modern crypto. Key triggers to migrate:

  • Compliance requirements (PCI, HIPAA, GDPR) that mandate stronger encryption or key management.
  • Support for multi-factor authentication and centralized policy enforcement that PPTP cannot natively provide.
  • Requirement for robust audit trails, granular access control, and split-tunneling policies.

Deploying PPTP can be a fast way to grant remote ERP access to employees when speed is essential. However, given protocol limitations, keep the deployment limited, monitor closely, and follow the hardening measures above. For long-term security and compliance, evaluate modern alternatives and plan a migration.

For more information on dedicated IP and VPN best practices, visit Dedicated-IP-VPN.