From 9c96e1f25cee28652a6ea6ec28709a7532a0237a Mon Sep 17 00:00:00 2001
From: medusa <newton214@gmail.com>
Date: Fri, 12 Apr 2024 12:28:46 +0000
Subject: [PATCH] Update docs/tech_docs/linux/vxlan.md

---
 docs/tech_docs/linux/vxlan.md | 63 ++++++++++++++++++++++++++++++++++-
 1 file changed, 62 insertions(+), 1 deletion(-)

diff --git a/docs/tech_docs/linux/vxlan.md b/docs/tech_docs/linux/vxlan.md
index 683305d..319d693 100644
--- a/docs/tech_docs/linux/vxlan.md
+++ b/docs/tech_docs/linux/vxlan.md
@@ -99,4 +99,65 @@ graph TD;
     A_Debian --- B_Debian
     B_Debian --- C_Debian
     C_Debian --- A_Debian
-```
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+```
+
+---
+
+Routing traffic from VXLAN tunnels between Linux bridges and potentially to an OPNsense gateway involves several steps, focusing on ensuring proper encapsulation, decapsulation, and routing of packets. Here’s a detailed approach to handle this scenario effectively:
+
+### 1. **Handling VXLAN Traffic on Linux Hosts**
+
+When dealing with VXLAN tunnels on Linux, the key aspect is managing how traffic is encapsulated and decapsulated. This process typically involves:
+
+- **Creating VXLAN Interfaces**: As discussed earlier, each Linux host will have a VXLAN interface configured. This interface encapsulates outgoing traffic and decapsulates incoming traffic based on the VXLAN Network Identifier (VNI).
+
+- **Bridging VXLAN and Ethernet Interfaces**: Often, it might be necessary to bridge the VXLAN interface with one or more physical or virtual Ethernet interfaces. This setup allows all interfaces in the bridge to communicate as if they were in the same physical network segment.
+
+```bash
+sudo ip link add name br0 type bridge
+sudo ip link set br0 up
+sudo ip link set eth0 up
+sudo ip link set vxlan0 master br0
+sudo ip link set eth0 master br0
+```
+
+This command sequence sets up a bridge `br0` and adds both the Ethernet interface `eth0` and the VXLAN interface `vxlan0` to this bridge.
+
+### 2. **Routing Traffic Between Bridges**
+
+To route traffic between different Linux bridges, which might be in different network namespaces or on different hosts:
+
+- **Configure IP Forwarding**: Make sure IP forwarding is enabled on the Linux hosts to allow traffic to be routed between interfaces.
+
+```bash
+echo 1 | sudo tee /proc/sys/net/ipv4/ip_forward
+```
+
+- **Set Up Routing Rules**: If the bridges are in different subnets, set up static routing rules or use dynamic routing protocols to manage the routes.
+
+```bash
+sudo ip route add 192.168.2.0/24 via 192.168.1.2 dev br0
+```
+
+This command tells the system how to find the 192.168.2.0/24 network via the next-hop IP address 192.168.1.2, which is accessible via the `br0` bridge interface.
+
+### 3. **Integrating with OPNsense**
+
+If you need to route traffic from the VXLAN to an OPNsense gateway, the approach will depend on whether the OPNsense device is acting as the edge router for the VXLAN network or if it's just another node within the network:
+
+- **As an Edge Router**: Ensure that the OPNsense has routes back to the VXLAN network and that NAT (Network Address Translation) settings are configured if needed. This is especially important if the VXLAN IPs are not part of the routable address space managed by OPNsense.
+
+- **NAT Configuration**: Configure NAT on OPNsense to allow devices outside the VXLAN (like the internet or other corporate networks) to communicate with devices inside the VXLAN.
+
+- **Firewall Rules**: Modify firewall rules in OPNsense to allow traffic from the VXLAN networks. This can involve allowing specific ports or entire subnets.
+
+### 4. **Debugging and Validation**
+
+- **Use tools** like `ping`, `traceroute`, `tcpdump`, and `ip link` to test connectivity and monitor the traffic to ensure that the routing and bridging are configured correctly.
+- **Monitoring VXLAN Traffic**: You can monitor VXLAN traffic specifically using `tcpdump` by filtering VXLAN traffic:
+
+```bash
+sudo tcpdump -ni any 'port 4789'
+```
+
+This setup provides a robust configuration for managing traffic flow between VXLAN segments, other network bridges, and an OPNsense gateway. Each step ensures that traffic is correctly managed, encapsulated, or decapsulated, and securely routed according to your network policies.
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