> For the complete documentation index, see [llms.txt](https://platform9.com/kb/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://platform9.com/kb/pmo/solution/instance-fails-to-reach-or-resolve-external-addresses.md).

# Instance Fails to Reach or Resolve External Addresses

## Problem

* One or more instances on a network are failing to reach or resolve any external addresses and IPs, e.g.

{% tabs %}
{% tab title="None" %}

```none
~ # rpm -Uvh https://yum.postgresql.org/11/redhat/rhel-7-x86_64/pgdg-redhat-repo-latest.noarch.rpmRetrieving https://yum.postgresql.org/11/redhat/rhel-7-x86_64/pgdg-redhat-repo-latest.noarch.rpmcurl: (6) Could not resolve host: yum.postgresql.org; Unknown errorerror: skipping https://yum.postgresql.org/11/redhat/rhel-7-x86_64/pgdg-redhat-repo-latest.noarch.rpm - transfer failed
```

{% endtab %}
{% endtabs %}

{% tabs %}
{% tab title="None" %}

```none
~ # ping www.google.com^C~ # ping 8.8.8.8PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.^C--- 8.8.8.8 ping statistics ---4 packets transmitted, 0 received, 100% packet loss, time 2999ms
```

{% endtab %}
{% endtabs %}

## Environment

* Platform9 Managed OpenStack - All Versions
* Neutron

## Cause

The default security group is not applied and/or does not allow for outbound access to the targeted CIDR(s).

## Resolution

1. [Edit the security groups for the instance](https://docs.platform9.com/openstack/virtual-machines-edit-instances-security-groups).
2. [Edit the security group(s)](https://docs.platform9.com/openstack/networks-security-group-mgmt) if needed to allow for outbound access.

If a security group is applied which allows for outbound access and the instance is still unable to send outbound traffic – please refer to: [Outbound Connectivity Failing for Instances on Tenant Network](https://support.platform9.com/hc/en-us/articles/360042790633).


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters:

```
GET https://platform9.com/kb/pmo/solution/instance-fails-to-reach-or-resolve-external-addresses.md?ask=<question>&goal=<user_goal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `build a script that syncs our docs to a CMS` lets GitBook tailor the answer to that use case.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.