Lightsail instance becomes unreachable from network

Question

I have an Ubuntu instance on Lightsail, located in region `eu-west-2a` (London Zone A). Since 2 months ago, about every 2 weeks, the instance just spontaneously becomes unreachable from network. This doesn't affect only network traffic coming from outside, but even network traffic from the Lightsail console itself: SSH connection doesn't work, the "Reboot" button doesn't work (it has no effect), the "Stop" button changes the status to "Stopping" for a long time, and the "Force Stop" button also seems to not have any effect. The "instance status check" metric shows a failure on every check. From the other metrics, this isn't caused by any exceptional use of resources (CPU, incoming traffic, outgoing traffic).

From the instance `systemd` journal, and other internal logs, I know that the instance still runs as usual while this happens, just "offline" (unable to reach the network, including AWS internal network - e.g. Amazon SSM Agent fails in `EC2RoleProvider`).

During these 2 months I have upgraded my Ubuntu 20.04 instance to an Ubuntu 24.04 instance, but the problem persists. It's a totally new instance, except it's located in the same region, having the same static IP address, and running the same applications.

What can be done about it?

re:Post Agent · Answer

The issue you're experiencing with your Lightsail instance becoming periodically unreachable is concerning and can be caused by several factors. Based on the information provided, here are some potential causes and steps you can take to address the problem:

1. Hardware or Host Issues: Since the problem persists even after upgrading to a new instance, it's possible there might be underlying hardware or host-level issues in the specific availability zone you're using.

2. Network Configuration: There could be intermittent network issues or misconfigurations affecting your instance's connectivity.

3. Resource Exhaustion: Although you mentioned that resource usage doesn't seem exceptional, there might be brief spikes or issues not captured in the metrics you're observing.

To troubleshoot and potentially resolve this issue:

1. Change Availability Zone: Consider creating a new instance in a different availability zone within the same region. This could help determine if the issue is specific to the current zone.

2. Monitor Detailed Metrics: Use Amazon CloudWatch to set up more detailed monitoring of your instance. This might reveal patterns or issues not visible in the standard metrics.

3. Check System Logs: When you regain access to the instance, thoroughly examine all system logs, including kernel logs, for any errors or warnings that might indicate the cause of the connectivity loss.

4. Create a Snapshot and Redeploy: Before the next occurrence, create a snapshot of your instance. If the issue happens again, try deploying a new instance from this snapshot in a different availability zone.

5. Network Interface Check: Investigate if there are any issues with the network interface of your instance. Sometimes, network interface problems can cause connectivity issues.

6. Contact AWS Support: If the problem persists after trying these steps, it would be advisable to contact AWS Support. They can investigate deeper issues that might not be visible at the user level, such as potential problems with the underlying infrastructure.

7. Consider EC2: If Lightsail continues to be problematic, you might want to consider migrating to an EC2 instance, which offers more configuration options and potentially better isolation from other tenants.

Remember to document each occurrence of this issue, including exact times and any observable patterns, as this information can be crucial for diagnosing the root cause.  
**Sources**  
[AWS lightsail need reboot every ten hours | AWS re:Post](https://repost.aws/questions/QU5ndEMvwFTtCK_jVFK--etw/aws-lightsail-need-reboot-every-ten-hours)  
[Troubleshoot status check failures on an unreachable EC2 Linux instance | AWS re:Post](https://repost.aws/knowledge-center/ec2-linux-status-check-failure)  
[Lightsail instance keeps timing out | AWS re:Post](https://repost.aws/questions/QUg3IVFyPIRvqgmKvhFphRzw/lightsail-instance-keeps-timing-out)  
[Lightsail SSH connect timing out | AWS re:Post](https://repost.aws/questions/QU9qGcOM9jRUm-8kiyTZHcXg/lightsail-ssh-connect-timing-out)

Lightsail instance becomes unreachable from network

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