Policy-Based Routing Via Two Networks on a Windows Machine

Policy-Based Routing via Two Networks on a Windows Machine

In this article, we will discuss the concept of policy-based routing on a Windows machine using two separate physical NICs (Network Interface Cards), each with its own IP address, and one of them routing VPN traffic via policy-based routing. This technique can be useful for a variety of scenarios, including network segmentation and multi-homed servers.

Understanding Policy-Based Routing

Policy-based routing is a technique that allows administrators to define rules that determine how network traffic is routed. These rules can be based on various factors, including the source or destination IP address, the type of traffic, or other network conditions. Policy-based routing can be used to route traffic through specific interfaces, networks, or devices based on the rules defined by the administrator.

Configuring Two Network Interfaces on a Windows Machine

To configure two network interfaces on a Windows machine, follow these steps:

1. Open the Network and Sharing Center.
2. Click on Change adapter settings on the left-hand side of the screen.
3. Right-click on an existing network interface and select Properties.
4. Select Internet Protocol Version 4 (TCP/IPv4) and click Properties.
5. Enter the IP address, subnet mask, and default gateway for the network interface.
6. Repeat steps 3-5 for the second network interface.

Configuring VPN Traffic via Policy-Based Routing

To configure VPN traffic via policy-based routing, follow these steps:

1. Open the Network and Sharing Center.
2. Click on Change adapter settings on the left-hand side of the screen.
3. Right-click on the VPN connection and select Properties.
4. Select the Networking tab.
5. Click on Internet Protocol Version 4 (TCP/IPv4) and click Properties.
6. Enter the IP address and subnet mask for the VPN connection.
7. Leave the default gateway blank.
8. Click OK to close the Properties dialog box.
9. Click Advanced.
10. Check the box for Use default gateway on remote network.
11. Click OK to close the Advanced dialog box.
12. Click OK to close the Properties dialog box.

Configuring Policy-Based Routing Rules

To configure policy-based routing rules, follow these steps:

1. Open the Command Prompt as an administrator.
2. Enter the following command:
``` route –p add mask metric ```
3. Replace the following variables:
• : the destination network address.
• : the subnet mask of the destination network.
• : the gateway address for the destination network.
• : the interface number of the network interface to route traffic through.
• : the metric value for the route.
4. Press Enter to create the policy-based routing rule.
5. Repeat steps 2-4 for additional rules.

Example Scenario

Suppose we have two network interfaces, one with an IP address of 192.168.1.1 and a subnet mask of 255.255.255.0, and the other with an IP address of 10.0.0.1 and a subnet mask of 255.255.255.0. We also have a VPN connection with an IP address of 172.16.0.1 and a subnet mask of 255.255.255.255.

We want to route traffic to the 192.168.1.0 network through the first network interface and traffic to the 10.0.0.0 network through the second network interface. We also want to route VPN traffic through the second network interface.

To configure policy-based routing rules for this scenario, we would enter the following commands:

These commands would create three policy-based routing rules:

• Traffic to the 192.168.1.0 network would be routed through the first network interface (interface 1).
• Traffic to the 10.0.0.0 network would be routed through the second network interface (interface 2).
• Traffic to the 172.16.0.0 VPN network would be routed through the second network interface (interface 2).

Policy-based routing is a powerful technique that can be used to route network traffic based on defined rules. By configuring two network interfaces on a Windows machine, administrators can route traffic through specific interfaces based on the destination network address. Adding VPN traffic to the mix can further extend the flexibility of policy-based routing.

References

• Microsoft Docs: Policy-Based Routing
• TechTarget: Policy-Based Routing
• Cisco: Policy-Based Routing Configuration Guide