> For the complete documentation index, see [llms.txt](https://docs.duplocloud.com/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.duplocloud.com/docs/automation-platform/overview/use-cases/hosts-vms/disable-source-destination-check.md).
# Disable Source Destination Check
Disable CloudFormation's SourceDestCheck in EC2 Host metadata
{% hint style="danger" %}
Source/destination checking is a security feature. Disabling it is only needed in specific use cases. In most cases, disabling it creates a security gap. We recommend consulting with the DuploCloud team before using this.
{% endhint %}
AWS EC2 ensures that each instance is either the source or the destination of any network traffic that it receives. This is called "[source/destination checking](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-eni.html#eni-basics)". In the DuploCloud Portal, this parameter is specified as `true`, by default, enabling source and destination checks.
There are times when you may want to override this default behavior, such as when an EC2 instance runs services [Network Address Translation (NAT)](https://docs.aws.amazon.com/vpc/latest/userguide/work-with-nat-instances.html#EIP_Disable_SrcDestCheck), routing, or firewalls. To override the default behavior and set the `SourceDestCheck` parameter to `false`, use this procedure.
## Disable `SourceDestCheck` in the DuploCloud Portal
Set `SourceDestCheck` to `false` for an EC2 Host:
1. In the DuploCloud Portal, navigate to **Cloud Services -> Hosts**.
2. In the **EC2** tab, select the Host for which you want to disable `SourceDestCheck`.
3. Click the **Metadata** tab.
4. Click **Add**. The **Add Metadata** pane displays.
Add Metadata pane for Key SourceDestCheck
5. In the **Key** field, enter **SourceDestCheck**.
6. In the **Value** field, enter **False**.
7. Click **Create**. The **Key**/**Value** pair is displayed in the **Metadata** tab.
EC2 Host page Metadata tab displaying SourceDestCheck Value of False
---
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