Kentik Detect has long offered the ability to resolve IP addresses to domain names. When Enable Reverse DNS Lookups is on (shown below left; see the Knowledge Base topic on Query Advanced Options), the domain names are displayed next to the addresses in any table returned from a query using source and/or destination IP address as a group-by dimension.

But our public DNS lookup obviously isn’t able to resolve IP addresses in a private (RFC 1918) namespace. Until now that has resulted in the display of a hyphen (”-”) where the names associated with a private address would otherwise be (see below right).

We’ve now addressed this with Custom DNS, a feature that enables you to designate one or more DNS servers for Kentik Detect to use for reverse lookups instead of our default public DNS server. The result is that the names associated with IP addresses will be displayed according to your designated reverse DNS servers rather than the Kentik-default DNS server. Using your dedicated DNS servers will result in Kentik Detect being able to display not only public but also private names.

Configuring Custom DNS is very straightforward, involving just a few clicks. Navigate to Admin » Custom DNS, where you’ll find the Custom DNS page shown below. In the callout near the top of the page you’ll see the IP address from which Kentik will query your designated DNS servers; you’ll need to be sure that the servers you designate are configured to allow queries from this address. Enter the IP of a DNS server into the Add DNS IP field, then click the Add button. If the IP address is valid then it will be added to the DNS Servers list at right. You can add multiple DNS servers to the list and queries from Kentik will be evenly distributed across the set.

After configuring a DNS server, you can use the Verify Reverse DNS Lookup button to open a dialog (shown below) in which you can test the lookup of any IP address.

For additional information, please refer to the Custom DNS article in the Knowledge Base. As always, for further information or help you can also contact the Kentik Customer Success team at support@kentik.com.