oe7drt-website/content/posts/2024/70-stalled-ssh-connections/index.md

---
title: Stalled SSH connections
summary: >
  My pfSense removed valid connections obviosly.
  This is how I solved it.
  <small>The thumbnail was created with Google AI (Imagen 3).</small>
date: 2024-10-06T19:30:17+02:00
lastmod: 2024-12-17T17:24:02+0000
categories:
  - computerstuff
tags:
  - networking
  - pfSense
  - openssh
  - selfhost
---

I spent some time adjusting my SSH configuration because I often get stalled
connections to my servers but I never got that fixed until recently, when I
started looking in my firewall settings on the pfSense.

After changing the <kbd>Firewall Optimization Settings</kbd> within
<kbd>System</kbd> → <kbd>Advanced</kbd> → <kbd>Firewall & NAT</kbd> to
<kbd>Conservative</kbd> I had no more of these hangs of my SSH sessions.

![pfSense settings](pfsense-netopt-settings.png)

I use the `ControlMaster` setting in my SSH configuration so the stalled
connections have to be killed with something like

```console
$ ssh -O exit {short hostname}
```

every time -- which is annoying.

{{< alert "triangle-exclamation" >}}
**Update on December 17 2024:**  
A few changes to the SSH configuration on client and server have been made.
{{< /alert >}}

It got better, but I still experience the one or other hang.

I added/modified these entries within `Host *` in
<kbd>~/.ssh/config</kbd> on the client:

```apache
ServerAliveInterval 100
ServerAliveCountMax 10000
```

and made these changes/additions in <kbd>/etc/ssh/sshd_config</kbd>
on the server:

```apache
ClientAliveInterval 60
ClientAliveCountMax 10000
TCPKeepAlive yes
```