> 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/tests/bgp-tests/monitoring-a-single-prefix.md).

# Monitoring a Single Prefix

Create a standalone BGP test when you want to monitor a specific prefix. The test collects routing information from BGP monitors and shows prefix reachability, autonomous system (AS) paths, and routing changes. For an overview of the capability and its use cases, see [BGP Monitoring](https://docs.thousandeyes.com/product-documentation/tests/bgp-tests).

## Before You Begin

Before you create the test:

* Identify the IPv4 or IPv6 prefix that you want to monitor. Enter the prefix and prefix length in Classless Inter-Domain Routing (CIDR) notation, for example, `198.51.100.0/24`.
* Decide whether to include covered prefixes. A covered prefix is a more specific prefix within the target prefix.
* If you want routing visibility from your own network, [configure a private BGP monitor](https://docs.thousandeyes.com/product-documentation/tests/bgp-tests/private-bgp-monitoring#configuring-a-private-bgp-monitor).
* Create any BGP alert rules that you want to assign to the test. For alert conditions and configuration guidance, see [Configuring BGP Alerts](https://docs.thousandeyes.com/product-documentation/tests/bgp-tests/bgp-alerts).

Standalone BGP tests collect routing data continuously and do not support instant tests. Data for the target prefix is typically available within five minutes after you create a test. If you enable **Include covered prefixes**, covered prefixes can take up to three hours to appear.

## Understanding Monitor Selection

IPv4 tests use IPv4 BGP monitors, and IPv6 tests use IPv6 BGP monitors. The BGP route visualization therefore shows only monitors that support the address family of the target prefix.

ThousandEyes ingests routing data from dozens of global BGP collectors and supports the following sources of BGP routing data:

* Public BGP monitors use publicly available routing data to provide internet-wide visibility, including data from RIPE Routing Information Service (RIS).
* ThousandEyes BGP monitors are configured and supported by ThousandEyes.
* Private BGP monitors are BGP peers that you connect to the ThousandEyes infrastructure to provide routing data from your own network.

You can use public monitors, private monitors, or both for the same test.

## Creating a BGP Test

1. In ThousandEyes, go to **Routing > Test Settings**.
2. Select **Start Monitoring**, and then select **Monitor a single prefix**.
3. Enter the **Prefix** that you want to monitor in CIDR notation, for example, `198.51.100.0/24`.
4. (Optional) To include prefixes that are covered by the prefix you entered, enable **Include covered prefixes**.
5. Review the BGP monitors used by the test. All public BGP monitors are included automatically.
   * **Public BGP Monitors**: This option specifies whether the test uses ThousandEyes public BGP Monitors to monitor target prefixes.
   * **Private BGP Monitors**: This dropdown allows you to select which private BGP Monitors monitor target prefixes.
6. To configure alerting:

   1. Enable **Alerts**.
   2. Select one or more BGP alert rules from the alert-rule dropdown.
   3. To manage alert-rule settings, select the settings icon next to the menu.

   For more information, see [Alerts](https://docs.thousandeyes.com/product-documentation/alerts).
7. (Optional) Add tags to the test.
   1. Under **Tags**, select **+ Add**.
   2. In the **Tags** dialog, do one of the following:
      * **Select an existing tag**: Search for the tag or browse the list, then select the check box next to the tag.
      * **Create a new tag**: Under **Create New Tag**, enter a **Key** and, optionally, a **Value**, and then select **Save**. The new tag is added to the test.
   3. When you finish selecting or creating tags, select **Save**.
8. (Optional) Enter a **Test name**.

   If you do not specify a name, ThousandEyes uses the **Prefix** value.
9. (Optional) Enter a **Description** to provide additional context for the test.
10. Select **Deploy** to create the test.

## Reviewing BGP Test Results

A BGP test provides the following views:

* **BGP Route Visualization** shows the AS paths from the selected BGP monitors to the target prefix. It includes routing and geographic information about each node and connection and identifies relevant events on the timeline and in the AS graph. For details, see [Visualizing BGP Routes](https://docs.thousandeyes.com/product-documentation/tests/bgp-tests/using-the-bgp-route-visualization-view).
* **BGP Updates** includes updates for all prefixes monitored by your account, real-time BGP message streaming, advanced filtering that includes RPKI status, and up to 30 days of historical data. Use it to investigate announcements, withdrawals, BGP community propagation, route changes, and other routing anomalies. For details, see [Using the BGP Updates Table](https://docs.thousandeyes.com/product-documentation/tests/bgp-tests/using-the-bgp-updates-table).

These views can help you detect routing anomalies, validate traffic-engineering changes, and investigate security events such as route leaks and route hijacks.

## Collecting BGP Data with Other Tests

You do not need a standalone BGP test to collect BGP data for every target. Tests that include network measurements can add BGP routing data as a configurable layer beneath their service, network, and path views.

* For a test that targets a service URL, ThousandEyes tracks reachability and path changes for the relevant prefixes.
* For a test that targets an IP address, ThousandEyes monitors the associated internet-routed prefix.
* In a supported test's network settings, enable **Collect BGP data** to make the BGP route visualization available. You can then configure the public and private BGP monitors used for the visualization.

For more information about configuring data collection for supported tests, see [Working with Test Settings](https://docs.thousandeyes.com/product-documentation/tests/working-with-test-settings).

## Learn More

* To monitor multiple prefixes associated with an AS, see [Monitoring Multiple Prefixes for an Autonomous System (AS)](https://docs.thousandeyes.com/product-documentation/tests/bgp-tests/monitor-multiple-prefixes).
* To define alert conditions for the test, see [Configuring BGP Alerts](https://docs.thousandeyes.com/product-documentation/tests/bgp-tests/bgp-alerts).
* To add routing perspectives from your network, see [Private BGP Monitoring](https://docs.thousandeyes.com/product-documentation/tests/bgp-tests/private-bgp-monitoring).