troubleshooting upgrade

README.md

@@ -86,7 +86,7 @@ I was getting frustrated at being forced to choose between being connected to my
 
 *Netflix blocking my connections that it sees coming from a DigitalOcean droplet*
 
-In Mistborn, Gateways are upstream from the VPN server so connections to third-party services (e.g. Netflix, Hulu, etc.) will appear to be coming from the public IP address of the Gateway. I setup a Gateway at home, then all VPN profiles created with this Gateway will apear to be coming from my house and are not blocked. No port-forwarding required (assuming Mistborn is publicly accessible).
+In Mistborn, Gateways are upstream from the VPN server so connections to third-party services (e.g. Netflix, Hulu, etc.) will appear to be coming from the public IP address of the Gateway. I setup a Gateway at home, then all VPN profiles created with this Gateway will appear to be coming from my house and are not blocked. No port-forwarding required (assuming Mistborn is publicly accessible).
 
 ![Mistborn Gateway Diagram](https://gitlab.com/cyber5k/public/-/raw/master/graphics/gateway_network.png)
 
@@ -268,6 +268,15 @@ Be sure to restart Docker afterward:
 sudo systemctl restart docker
 ```
 
+## Troubleshooting Upgrading from Ubuntu 18.04 to 20.04
+Owing to changes in docker NAT rules and container DNS resolution, some Wireguard client configurations generated with Mistborn before updates on 25 April 2020 may experience issues after upgrading to Ubuntu 20.04 LTS. Symptoms: can ping but can't resolve DNS.
+
+Solution: Edit the Wireguard client config and set:
+```
+DNS = 10.2.3.1
+```
+Close the config and restart Wireguard.
+
 # Technical and Security Insights
 These are some notes regarding the technical design and implementations of Mistborn. Feel free to contact me for additional details.