Devices utilizing a Mac OS X computer running Internet Sharing are unable to perform DNS resolution when the Cisco Umbrella roaming client is installed on a Mac. This is true for all versions of OS X.
The Internet Sharing feature of Mac OS X essentially has your computer act as a wireless router. This means that your computer also becomes a DHCP and DNS server. When Internet Sharing is first enabled, the computer tries to start a DNS server. The DNS server attempts to bind to 127.0.0.1:53 and *YourPrivateIPAddressHere*:53.
The Umbrella roaming client works by binding to 127.0.0.1:53, and therefore conflicts with Internet Sharing. The Internet Sharing feature will turn on; however, any devices that connect to the computer with Internet Sharing will not have DNS resolution.
In order for Internet Sharing to work, do one of the following:
- Recommended—Typically, you would not be using your Mac OS X computer as an Internet Sharing device for many other devices (unlike a traditional router), it's easy to adjust the second computer/device once it has connected to Mac with Internet Sharing. The second computer/device should be set to use other DNS servers, such as Umbrella. We have articles for how to configure DNS individually on devices.
- Not Recommended—Temporarily stop the Umbrella roaming client before turning on Internet Sharing. Re-enable the Umbrella roaming client once finished.