> For the complete documentation index, see [llms.txt](https://docs.thousandeyes.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.thousandeyes.com/product-documentation/global-vantage-points/enterprise-agents/configuring/configuring-rdns-lookups-for-enterprise-agents.md).

# Configuring rDNS Lookups for Enterprise Agents

A reverse DNS lookup or resolution (rDNS) queries the Domain Name System (DNS) to determine the domain name associated with an IP address. This is the opposite of a standard DNS lookup, which determines the IP address associated with a domain name.

ThousandEyes Enterprise Agents perform rDNS lookups for [RFC 1918](https://datatracker.ietf.org/doc/html/rfc1918) addresses by default. The agent performs lookups for each hop in the path, until it encounters a non-RFC 1918 address, or one that is not in the configured rDNS ranges.

This article provides the steps to extend rDNS lookups by the agent for public IP addresses.

## Prerequisites

* One or more ThousandEyes Enterprise Agents or clusters.

## Configuration

To configure the agent's reverse DNS behavior:

1. In the ThousandEyes web app:
   * For Enterprise Agents, navigate to **Network & App Synthetics > Agent Settings > Enterprise Agents > Agents**.
   * For clusters, navigate to **Network & App Synthetics > Agent Settings > Enterprise Agents > Clusters**.
2. Click the Enterprise Agent or cluster you wish to configure to open the **Edit Configuration** panel.
3. Open the **Advanced Settings** tab.
4. In the **Reverse DNS** section, add the public IP ranges that should be used for the rDNS lookups.

![](https://1112912342-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-M4QARF6s57qxMrOHDTZ%2Fuploads%2Fgit-blob-b89ed013312711f4ad101de8394990dbce281232%2Fadvanced-settings_rdns-config.png?alt=media\&token=3bc609d1-5046-497b-a8e1-74a028132ff2)

5. After adding the ranges, click **Save Changes**.

To configure multiple Enterprise Agents at once:

1. Navigate to **Cloud and Enterprise Agents > Agent Settings > Enterprise Agents > Agents**.
2. Select the checkbox beside each desired Enterprise Agent, or the checkbox beside **Agent Name** to select all.
3. From the bottom configuration options panel, open the **Edit** menu and select **Edit Reverse DNS**.

![](https://1112912342-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-M4QARF6s57qxMrOHDTZ%2Fuploads%2Fgit-blob-b2a9c5a7afdfcb0ec48bf505bb4d18c91e73f9d7%2Fmulti-agent-config_rdns_1.png?alt=media\&token=d860ebb8-efe8-4660-b5a7-39581922f493)

4. In the **Reverse DNS** side panel, configure the public IP ranges, and click **Save Changes**.

![](https://1112912342-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-M4QARF6s57qxMrOHDTZ%2Fuploads%2Fgit-blob-6a113213d456ea94c4973d971e87008a55bdc6df%2Fmulti-agent-config_rdns_2.png?alt=media\&token=543f95ad-784c-46c5-82d0-694333b4a665)

Once configured, the domain name for each hop will be displayed in the Path Visualization. Hover the cursor over the node to see that node's details:

![](https://1112912342-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-M4QARF6s57qxMrOHDTZ%2Fuploads%2Fgit-blob-68a72e1565c68ce4789a46030e5bb66556c9e7c2%2Fadvanced-settings_rdns-path-vis.png?alt=media\&token=aec5fd67-c812-4304-bede-5193a46269a2)