Point-to-Point Tunneling Protocol (PPTP) implements virtual private networks by bypassing the network firewall. It’s older and not as secure as some of the newer protocols, but it still has a place in many business environments. 

PPTP is often easier to set up and can be beneficial for certain legacy applications that don't require the highest levels of encryption. Though not ideal if you handle sensitive information, it provides a straightforward way for remote users to access the network.

How PPTP Passthrough works

PPTP Passthrough allows PPTP traffic to bypass or pass through your network's firewall. It works like a gatekeeper who knows when to let certain data packets in and out. 

Say you’re working from home, and you need to access some files on your company’s server. Your company might also be using a PPTP VPN for secure connections. If your home router doesn’t support PPTP Passthrough, the connection might fail. Your VPN traffic can get blocked by the router's firewall. 

PPTP uses two types of communication: TCP port 1723 for the initial connection and GRE (Generic Routing Encapsulation) for the data packets. Many routers aren't configured to handle GRE packets by default. Some might even block GRE traffic if not properly set up. To get around this, the router needs to support PPTP passthrough.

When you enable PPTP passthrough on your router, you’re telling it to recognize and allow traffic associated with PPTP. This includes opening up the necessary TCP port and properly handling GRE packets, so they don’t get dropped or misrouted. 

For example, if your company's remote employees connect to your network via a PPTP VPN, enabling PPTP passthrough ensures their connection doesn't get interrupted by the router's firewall.

Without PPTP passthrough, connections might drop or fail to initiate, leading to frustrated users and lost productivity. In practice, many modern routers have this feature built-in and can be enabled with just a few clicks in the router's settings interface. 

Therefore, when setting up your company network, always check if your router supports PPTP passthrough and ensure it's enabled. Many popular router brands, like Netgear and Linksys, offer this feature. It’s usually enabled by default, but you should check your router’s settings to make sure.

Why PPTP is still used in company networks

PPTP Passthrough is useful for businesses that rely on secure remote connections. These businesses usually have employees who need to access the company's internal network from home or while traveling. 

PPTP allows those remote employees to connect securely. It creates a 'tunnel' through which data can travel safely, shielding sensitive information from prying eyes.

Quick and easy setup process

Setting up PPTP is less complex than with other VPN protocols. This simplicity means less time spent on configuration and troubleshooting. You can have a VPN for a small remote team set up in a couple of hours.

Cross-platform compatibility

Whether your team is using Windows, Mac, or even some Linux distributions, PPTP is often natively supported. This cross-platform compatibility can save you from a lot of headaches. 

Take, for instance, a scenario where a company uses a mixed environment with different operating systems. With PPTP, there’s no need for additional software installations, which makes onboarding new employees much smoother.

PPTP Passthrough is also vital for allowing these secure connections through routers that might otherwise block VPN traffic. Without it, employees could find themselves unable to connect to the network from certain locations, like hotels or cafes with strict firewall rules.

PPTP is particularly handy in high-availability network environments. For example, if a company relies on continuous access to its servers for customer service operations, any downtime could be disastrous. PPTP helps ensure that remote maintenance and troubleshooting can be done swiftly, minimizing potential downtime.

VPN usage in corporate environments

VPNs ensure secure and private communication over public networks. They allow team members working remotely to access your company's internal network securely. You can share sensitive documents and resources as if you were on the same local network.

VPNs create a private, encrypted tunnel specifically for their data. This encryption makes it incredibly difficult for unauthorized users to eavesdrop on their communications. There are other benefits of using VPN in enterprise networks:

Enables access to geo-restricted content and services

You can use VPNs to bypass geo-restrictions. Sometimes, you need to access region-specific content or services that are only available in certain countries. By connecting to a VPN server in the desired location, you gain access to these resources without hassle.

Assists in regulatory compliance

VPNs also play a critical role in maintaining compliance with data protection regulations. Many industries have strict guidelines for data security, and VPNs help ensure that sensitive information remains safeguarded. Whether it’s client data in finance or patient records in healthcare, a VPN adds an extra layer of security.

Facilitates remote IT support

IT departments often utilize VPNs for remote management of corporate devices. If you need to troubleshoot an employee's laptop, you can connect to it via a VPN and perform necessary tasks as if you were physically present. This can be a real time-saver and increases efficiency significantly.

In essence, VPNs are versatile tools in corporate environments. They provide secure access to resources, protect data over public networks, help in regulatory compliance, and facilitate remote IT support.

Role of NAT (Network Address Translation) in PPTP Passthrough

NAT allows multiple devices on a local network to share a single public IP address when accessing the internet. If you're in a big office with only one key to the front door, NAT is like the receptionist who handles the key, ensuring everyone gets in and out without a fuss.

Now, when it comes to PPTP passthrough, NAT needs to handle GRE (Generic Routing Encapsulation). GRE is the messaging system PPTP uses to communicate securely. 

NAT is excellent when handling regular traffic, but GRE is a bit different. So, for PPTP to work smoothly, your NAT device (like a router) needs to know how to manage GRE packets.

Let’s say you’re working from home and need to connect to your company’s network using PPTP. Your home router, which uses NAT, has to pass through your VPN traffic, including those tricky GRE packets. If it doesn’t handle GRE properly, you might struggle to connect to your company’s network. 

Some routers have the PPTP passthrough feature, which means they are configured to handle GRE and other related traffic without issues. So, if you encounter problems connecting to a VPN, a quick toggle of the "PPTP passthrough" setting on your router should fix it.

Enabling PPTP Passthrough on different router brands

To enable PPTP passthrough on different router brands, you typically need to tweak a few settings. Here’s how you can do it on some popular models.

TP-Link routers

A router like the TP-Link Archer AX1800 doesn't support WireGuard, so you have to rely on PPTP. To enable PPTP on the router, navigate to the virtual servers and ensure to forward port 1723. 

Your initial attempts may fail because PPTP requires more than just port 1723; it also relies on GRE (protocol 47), which isn't always straightforward to configure on TP-Link routers.

Netgear routers

Netgear routers, like the R6260, can be a bit more complex. Setting up PPTP passthrough requires you to dive into the advanced settings and look for options related to VPN passthrough. 

Ensure that both PPTP and GRE passthrough are enabled. If you run into issues, sometimes the firmware might be at fault. You may have to downgrade the firmware to get the passthrough working correctly.

Asus routers

Enabling PPTP passthrough is easier on Asus routers. On the router’s interface, go to the WAN settings and look for the "VPN Passthrough" section. Make sure the PPTP passthrough option is enabled. Keep in mind that older routers might have hardware limitations that can affect VPN performance.

OpenWrt routers

Enabling PPTP passthrough on OpenWrt is a bit different. The flexibility of OpenWrt means you often need to install additional packages. For example, you may have to install `kmod-nf-nathelper-extra` to get PPTP working. 

After installation, make sure to adjust the firewall settings to allow traffic on port 1723 and protocol 47. This usually fixes issues commonly encountered on OpenWrt 19.07.7 setups. However, if you're still having trouble, checking the logs can provide insights into what might be blocking the traffic.

Each router has its quirks, and while the general process is similar, the exact steps can vary. Always ensure your firmware is up-to-date, and remember that PPTP isn’t the most secure, so use it cautiously.