Linux/DD-WRT iptables/route/policy based routing - static route wildcard domain to a different gateway
Introduction:
When it comes to networking, there are times when you may want to route traffic for a specific domain to a different gateway. This can be useful in situations where you want to prioritize or segregate traffic based on the domain name. In this article, we will explore how to achieve this using Linux/DD-WRT iptables/route/policy based routing.
Prerequisites:
Before we proceed, make sure you have the following:
- A Linux or DD-WRT router
- Basic knowledge of networking concepts
Step 1: Enable IP forwarding
First, we need to enable IP forwarding on our Linux or DD-WRT router. IP forwarding allows the router to forward packets from one network interface to another. To enable IP forwarding, open a terminal or SSH into your router and run the following command:
sudo sysctl -w net.ipv4.ip_forward=1
Step 2: Create static routes
Next, we need to create static routes to redirect traffic for the wildcard domain to a different gateway. To do this, we will use the route command. Open a terminal or SSH into your router and run the following command:
sudo route add -net {wildcard_domain_network} gw {new_gateway}
Replace {wildcard_domain_network} with the network address of the wildcard domain and {new_gateway} with the IP address of the new gateway.
Step 3: Configure iptables
Now, we need to configure iptables to ensure that the traffic is routed correctly. Iptables is a powerful firewall utility that allows you to manipulate network packets. Open a terminal or SSH into your router and run the following command:
sudo iptables -t nat -A PREROUTING -p tcp -d {wildcard_domain_network} -j DNAT --to-destination {new_gateway}
Replace {wildcard_domain_network} with the network address of the wildcard domain and {new_gateway} with the IP address of the new gateway.
Step 4: Set up policy-based routing
Finally, we need to set up policy-based routing to ensure that the traffic is routed based on our rules. Policy-based routing allows you to define routing rules based on various criteria, such as source IP address, destination IP address, or port number. Open a terminal or SSH into your router and run the following command:
sudo ip rule add from {your_ip_address} table {table_number}
Replace {your_ip_address} with your IP address and {table_number} with a unique table number.
Conclusion:
By following the steps outlined in this article, you should now be able to route traffic for a wildcard domain to a different gateway using Linux/DD-WRT iptables/route/policy based routing. This can be a powerful tool for network administrators who need to prioritize or segregate traffic based on domain names.
References:
| Source | Link |
|---|---|
| Linux man page - route | https://linux.die.net/man/8/route |
| Linux man page - iptables | https://linux.die.net/man/8/iptables |
| Linux man page - ip | https://linux.die.net/man/8/ip |