> For the complete documentation index, see [llms.txt](https://clients.medianova.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://clients.medianova.com/products/security/asn-blocking.md).

# ASN Blocking

Configure ASN Blocking to reject requests from specified autonomous systems.

Block requests from specified autonomous systems by configuring their Autonomous System Numbers (ASNs).

**ASN Blocking** evaluates the ASN associated with each incoming request and blocks traffic from configured ASNs. Blocked requests receive a `403` response at the CDN edge before cache lookup or origin forwarding.

ASN Blocking is configured for CDN Resources in the [Medianova Control Panel](https://cloud.medianova.com).

## Configure ASN Blocking

{% stepper %}
{% step %}

### Open Security

Open the CDN Resource that you want to configure and select **Security - Geo blocking**.
{% endstep %}

{% step %}

### Enable ASN Blocking

Turn on **ASN Blocking**.

<figure><img src="https://542970813-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FtK7oIwmhUHdEJcaH4Hx8%2Fuploads%2FEjM89qEncEGRKT0BaYov%2Fimage.png?alt=media&amp;token=5d3a4995-f663-49f7-b59b-22da59d0e441" alt=""><figcaption></figcaption></figure>
{% endstep %}

{% step %}

### Add Blocked ASNs

Under **Blocked ASN**, enter the ASN that you want to block and select **Add**.

ASN numbers can be entered with or without the `AS` prefix. For example:

* `AS13335`
* `13335`

Add additional ASNs as required.
{% endstep %}

{% step %}

### Save the Configuration

Select **Save** in the pending changes bar.

Review the pending changes and confirm the configuration.
{% endstep %}
{% endstepper %}

## How ASN Blocking Works

When ASN Blocking is enabled, the CDN evaluates the autonomous system number associated with each incoming request.

If the ASN is included in the blocked list:

* The request is rejected with an HTTP `403` response.
* The request is blocked at the CDN edge.
* Cache lookup is not performed.
* The request is not forwarded to the origin server.

## Manage Blocked ASNs

Configured ASNs are displayed under **Blocked ASNs**.

You can remove an individual ASN from the list or select **Clear all** to remove all configured ASNs. Save the CDN Resource configuration after making changes.

## Important Notes

* ASN Blocking uses a blocklist model. Only ASNs added to **Blocked ASNs** are rejected.
* ASN values can be entered with or without the `AS` prefix.
* Removing an ASN from the list allows it to stop being subject to this ASN-based block after the updated configuration is saved.

## Related Concepts

* [IP Restriction](/products/security/ip-restriction.md)
* [Geo Blocking](/products/security/geoblocking.md)
* [Security](/products/security.md)


---

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