diff --git a/docs/index.html b/docs/index.html
index f4d58f57..21531c72 100644
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+++ b/docs/index.html
@@ -178,6 +178,7 @@ grep '^# ' index.html | grep -v '<br' | tr '#' '-'
 - Deploying a local registry
 - Overlay networks
 - Breaking into an overlay network
+- Securing overlay networks
 
 ---
 
@@ -2601,6 +2602,130 @@ WHY?!?
 
 ---
 
+# Securing overlay networks
+
+- By default, overlay networks are using plain VXLAN encapsulation
+
+  (~Ethernet over UDP, using SwarmKit's control plane for ARP resolution)
+
+- Encryption can be enabled on a per-network basis
+
+  (It will use IPSEC encryption provided by the kernel, leveraging hardware acceleration)
+
+- This is only for the `overlay` driver
+
+  (Other drivers/plugins will use different mechanisms)
+
+---
+
+## Creating two networks: encrypted and not
+
+- Let's create two networks for testing purposes
+
+.exercise[
+
+- Create an "insecure" network:
+  ```bash
+  docker network create insecure --driver overlay --attachable
+  ```
+
+- Create a "secure" network:
+  ```bash
+  docker network create secure --opt encrypted --driver overlay --attachable
+  ```
+
+]
+
+.warning[Make sure that you don't typo that option; errors are silently ignored!]
+
+---
+
+## Deploying a web server sitting on both networks
+
+- Let's use good old NGINX
+
+- We will attach it to both networks
+
+- We will use a placement constraint to make sure that it is on a different node
+
+.exercise[
+
+- Create a web server running somewhere else:
+  ```bash
+    docker service create --name web \
+           --network secure --network insecure \
+           --constraint node.hostname!=node1 \
+           nginx
+  ```
+
+]
+
+---
+
+## Sniff HTTP traffic
+
+- We will use `ngrep`, which allows to grep for network traffic
+
+- We will run it in a container (because we can!)
+
+- We will use host networking to sniff the host's traffic
+
+.exercise[
+
+- Sniff network traffic and display all packets containing "HTTP":
+  ```bash
+  docker run --net host nicolaka/netshoot ngrep -tpd eth0 HTTP
+  ```
+
+]
+
+---
+
+## Check that we are, indeed, sniffing traffic
+
+- Let's see if we can intercept our traffic with Google!
+
+.exercise[
+
+- Open a new terminal
+
+- Issue an HTTP request to Google (or anything you like):
+  ```bash
+  curl google.com
+  ```
+
+]
+
+The ngrep container will display one `#` per packet traversing the network interface.
+
+When you do the `curl`, you should see the HTTP request in clear text in the output.
+
+---
+
+## Try to sniff traffic across overlay networks
+
+- We will run `curl web` through both secure and insecure networks
+
+.exercise[
+
+- Access the web server through the insecure network:
+  ```bash
+  docker run --rm --net insecure nicolaka/netshoot curl web
+  ```
+
+- Now do the same through the secure network:
+  ```bash
+  docker run --rm --net secure nicolaka/netshoot curl web
+  ```
+
+]
+
+When you run the first command, you will see HTTP fragments.
+<br/>
+However, when you run the second one, only `#` will show up.
+
+---
+
 # Rolling updates
 
 - We want to release a new version of the worker