> For the complete documentation index, see [llms.txt](https://docs.console.zenlayer.com/welcome/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.console.zenlayer.com/welcome/ip-transit/manage-ip-transit/add-cidr-block.md).

# Add CIDR Block

You can add CIDR blocks to a running instance on demand. The BGP announcement configuration updates automatically without interrupting your service.

## Prerequisites

* The instance is **Running**.

## Procedures

**Option 1: Instance list**

In the row of the target instance, click **Actions** > **Add CIDR Block**.

**Option 2: Instance detail page**

Go to the instance detail page, find the CIDR block section under **Network Configuration**, and click **Add**.

1. In the dialog, select the IP type and block size.
2. Click **Add CIDR Block** to confirm.

## Result

After submission, the instance enters **Processing** state while the new CIDR goes through the following stages:

**IP Allocation** → **IP Configuration** → **Complete**

When delivery succeeds, the instance returns to **Running**. The new CIDR block appears in the list and the BGP routing table on the edge router updates automatically.

{% hint style="info" %} <mark style="color:blue;">**Note**</mark>

* <mark style="color:blue;">You cannot perform other operations while the instance is in Processing state.</mark>
* <mark style="color:blue;">You need at least one public CIDR block. You can only delete a CIDR block if at least two are configured.</mark>
  {% endhint %}