ssh keeps dropping after changed internet provider

3 min read 22-10-2024

the ifix

ssh keeps dropping after changed internet provider

If you've recently switched your internet provider and are experiencing frequent SSH connection drops, you're not alone. This issue can be frustrating, especially if you rely on SSH for remote server management or file transfers. In this article, we'll explore the potential causes of these drops and provide actionable solutions to stabilize your SSH connections.

Understanding the Issue

When you change your internet provider, various factors can lead to connection instability. Some common problems that may cause SSH disconnections include misconfigured network settings, firewall issues, or Quality of Service (QoS) settings that prioritize certain types of traffic over others.

For instance, you may encounter a situation where the SSH session drops intermittently, leading to interruptions in your workflow. The original scenario can be summarized as follows:

"I changed my internet provider, and now my SSH connection keeps dropping."

Analyzing the Problem

Potential Causes

Network Configuration: Upon changing your ISP, your router might require a new configuration. This could include changes to the IP address, DNS settings, or gateway settings.
Firewall and Security Settings: Your new ISP may have different security measures that block certain ports. Ensure that port 22 (the default port for SSH) is open and allowed through the firewall.
QoS Settings: Some ISPs implement QoS to manage bandwidth distribution. If SSH traffic is deprioritized, your connection may suffer, leading to drops.
MTU Size Issues: Maximum Transmission Unit (MTU) settings can affect data packets. A mismatch in MTU settings can lead to fragmented packets, causing timeouts and disconnections.

Practical Solutions

Here are some practical steps to resolve SSH connection drops:

Check Network Configuration:
- Verify your router settings to ensure that they are configured correctly for your new ISP.
- You can find these settings under the "Internet" or "WAN" configuration in your router's administration panel.
Adjust Firewall Settings:
- Access your router's firewall settings and make sure that port 22 is open.
- If using a host-based firewall (like UFW or iptables), ensure that rules allow SSH traffic.
Adjust QoS Settings:
- Review your router's QoS settings and ensure that SSH traffic is prioritized.
- You can find these settings in the QoS configuration section of your router.
Configure MTU Size:
- Open your terminal and use the following command to check your current MTU size:
```
ip link show
```
- To change the MTU size, use:
```
sudo ip link set dev eth0 mtu 1400
```
- Test different sizes (e.g., 1400, 1500) to find one that works best.

Additional Considerations

Use KeepAlive Options: To help prevent SSH disconnections, you can modify your SSH client configuration by adding the following lines to your ~/.ssh/config file:
```
Host *
    ServerAliveInterval 60
    ServerAliveCountMax 30
```
This setting sends a keepalive message every 60 seconds, ensuring your connection remains active.
Consider Alternate Ports: If your ISP blocks port 22, you might want to configure SSH to use an alternative port (like 2222). This requires both server and client changes.

Conclusion

Experiencing SSH drops after switching internet providers can be a common issue, but it is usually resolvable with proper configuration. By following the troubleshooting steps outlined above, you can stabilize your SSH connections and ensure reliable remote access.

Useful Resources

By understanding the underlying issues and applying the appropriate fixes, you can overcome the connectivity challenges associated with your new ISP and maintain a stable SSH connection for your needs.