# Using the AS Details Screen

The **AS Details** screen gives you a single view of the routing state for one autonomous system (AS). You can use it to review announced prefix trends, monitoring coverage, and Resource Public Key Infrastructure (RPKI) status without switching between multiple screens.

## Opening the AS Details Screen

1. In the ThousandEyes, go to **Routing > AS Details**.
2. In **Search for AS Number**, enter an AS number.

   The screen loads the selected AS and updates the overview metrics, trend chart, and prefix table.

## Reviewing the AS Overview Section

![AS Details screen](/files/YZeX49tRzbBMwjpeEf8J)

In the **Overview** section, you can check high-level AS metrics at a glance:

* **IPv4 Prefixes** shows the number of announced IPv4 prefixes for the selected AS.
* **IPv6 Prefixes** shows the number of announced IPv6 prefixes for the selected AS.
* **AS Neighbors** is the number of unique neighbor relationships for the selected AS. ThousandEyes computes it by counting every adjacent pair of autonomous systems along canonical BGP paths in both directions. Each unique pair counts only once.

Use this section first when you want a quick baseline before you investigate individual prefixes.

## Using the Prefix Announcement Trend Chart

The **Prefix Announcement Trend** chart shows how the number of announced prefixes changes over time.

* Use the **IPv4** and **IPv6** selectors to focus on one address family.
* Use the chart to identify stable periods and any potential changes in announcement volume.
* Correlate trend changes with events in your routing workflow.

If you are troubleshooting an incident or looking for confirmation of a networking change you've made, check the chart as part of your workflow.

## Working with the Announced Prefixes Table

![Announced Prefixes table](/files/AE70hXGBQhbQkMQpHrqP)

The **Announced Prefixes** table provides prefix-level detail for the selected AS.

Use the table controls to focus your investigation:

* **Search** filters rows by prefix.
* The monitoring filter defaults to **Monitored: All**, which lists every prefix. Open the dropdown to select **Yes** (only monitored prefixes) or **No** (only unmonitored prefixes).

Use the table columns to validate status:

* **Prefix** identifies the announced network block.
* **Monitored** shows whether the prefix is monitored in your account.
* **Visible By** shows how many monitors can see the prefix.
* **RPKI Status** shows route origin validation status for the prefix.

Use pagination controls at the bottom of the table to move through large prefix sets.

## Monitoring Coverage and Alert Behavior

Monitoring and alerting behavior depends on whether prefixes in the selected AS are monitored in your account.

Alerts apply only to prefixes that are monitored in your account. For prefixes that are not monitored, enable monitoring first if you want alerts for those prefixes.

To set up monitoring for prefixes that are not monitored yet, select **Start Monitoring** from the **AS Details** screen.

## Next Steps

* To onboard prefixes from an AS, see [BGP Easy Onboarding](https://docs.thousandeyes.com/product-documentation/tests/bgp-tests/bgp-easy-onboarding).
* To inspect individual announcements and withdrawals seen by our monitors, see [Using BGP Updates](https://docs.thousandeyes.com/product-documentation/tests/bgp-tests/using-the-bgp-updates-table).
* To review route validation states, see [RPKI](https://docs.thousandeyes.com/product-documentation/tests/bgp-tests/rpki).


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