Contents

Introduction

Overview

Mozilla Firefox

Google Chrome

Caveats

Workarounds

Introduction

This document describes how Umbrella supports DNS over HTTPS (DoH), encrypting DNS queries for privacy.

Overview

Cisco Umbrella supports DNS over HTTPS (DoH), allowing DNS queries to be encrypted and protected from interception or modification. Use this DoH endpoint:

Hostname

Description

doh.umbrella.com

Frontend for Umbrella’s standard DNS service (208.67.222.222/220.220)

Steps for using DoH with Umbrella depend on your browser and operating system.

Mozilla Firefox

Details and instructions are available from Mozilla. Firefox can be configured to use Umbrella as a custom DNS over HTTPS provider.

1. Navigate to Options > General > Network Settings and select Enable DNS over HTTPS.

2. Under Use Provider, choose Custom and enter the URI template:

3. https://umbrella.cisco.com/doh-help

4. Select OK and your queries are encrypted.

Preferences.png

Google Chrome

Details and instructions on configuration are available from the Chromium Blog. Chrome automatically enables the use of DoH if Secure DNS is enabled and it sees Umbrella anycast IP addresses used by the operating system for DNS.

Configure your OS to use these IP addresses as DNS servers:

Service

IPv4 Addresses

IPv6 Adresses

Umbrella DNS

208.67.222.222

208.67.220.220

2620:119:35::35

2620:119:53::53

1. In the Chrome settings, navigate to Privacy and security >Security (Or enter chrome://settings/security into the address bar).

2. Enable Use secure DNS.

3. Your DNS queries are now encrypted. You can visit the Umbrella DoH Test Page to check your configuration.

Note: Chrome looks for the Umbrella IP addresses specifically when deciding whether to upgrade to DoH. This means if you are configured to use the IP address of a local DNS server or forwarder, Chrome cannot upgrade to using DoH, even if that server forwards to Umbrella.

If your computer is considered managed by Chrome, which is likely if your computer is provided to you by your work or school, it cannot auto-upgrade to using DoH, and this setting cannot be visible or configurable.

Instead of auto-upgrading based on IP, you can configure Umbrella directly by setting a custom provider. Under Use secure DNS, select With and choose Custom from the drop-down. Where it asks to enter custom provider, add the Umbrella URI template in this format:

https://doh.umbrella.com/dns-query

Caveats

There are some situations you can encounter that cause a conflict between DoH and Umbrella SWG (notably the AnyConnect module):

1. The External Domains feature in AnyConnect allows domains and IP addresses to bypass Umbrella SWG by going direct to the internet instead. It cannot be configured by domain name, or Frequently Qualified Domain Name (FQDN), when using DoH. This is because AnyConnect relies on the DNS cache in the operating system to link domain names to IP addresses when detecting which requests go to SWG and which bypasses it. When DOH is utilized (especially by a browser), the DNS stub resolver for the operating system is bypassed and consequently no DNS cache entry is created. This leaves AnyConnect unable to correlate a domain name or FQDN to bypass, with the packet it is seeing.

Workarounds

Disable DOH on workstations using AnyConnect for Umbrella SWG, and/or configure External Domains (SWG exceptions) by IP address instead of domain or FQDN.

2. If DoH is used for resolution of internal resources (such as example.local or example.corp) by an internal DNS server, AnyConnect Umbrella SWG must be configured to not intercept those DOH requests. This is because DoH looks like any other HTTPS request, and the SWG module intercepts it and redirects it to Umbrella. If the DoH server is not accessible from the Umbrella cloud, the query never reaches the destined internal DNS server.