SSH (dropbear) sessions keep dropping [solved]

[lhoekenga]

I've got an RT-AC88U recently upgraded to 386.2.4. My SSH sessions to the router drop after a few minutes..

Timeout, server 192.168.1.1 not responding.

I noticed this when pursuing some other issues. Prior to 386.2.4, I was running 386.1.2, and had similar problems.
Syslog says the session ended normally..

May 21 09:10:54 dropbear[9343]: Exit (router) from <192.168.1.72:58351>: Exited normally

Any ideas?
thanks!
Liam

 

[dave14305]

I used to see odd ssh behavior when I had AiProtection enabled. I couldn’t prove it, but the issue stopped after I disabled it.

 

[lhoekenga]

I did a factory reset and reinstalled the stock firmware (3.0.0.4_386_43129-g60defb2) and the SSH issue seemed to go away.
I did another factory reset and installed 386.2_6 (without restoring any preexisting configuration), and the issue came back.

SSH drops the connection pretty quickly (less than a minute), with this error message..

Timeout, server 192.168.1.1 not responding.

I had to install screen from entware just to be able to interact with amtm.

I have not tried downgrading to 384.

Liam

 

[L&LD]

Are you first flashing the firmware you want to use, then doing a full reset to factory defaults?

What you've written above suggests you're doing things in the wrong order.

 

[lhoekenga]

Are you first flashing the firmware you want to use, then doing a full reset to factory defaults?

Yes. I apologize if was unclear. I am first flashing the firmware and then doing a factory reset.

 

[lhoekenga]

I'm trying a different router. I'm seeing the same issue on a RT-AX88U running Merlin 386.2_6 - SSH to the router drops connection within a minute.
I upgraded to Merlin, did a factory reset and then reconfigured everything.
I didn't see the issue on stock (3.0.0.4.386.42820).

I've tried disabling SSH timeouts in the web GUI, but it hasn't helped. I am concerned that if it's dropping SSH connections, that it might be killing other connections.

Liam

 

[archiel]

As you are getting the same result on two different routers, could the issue be with your SSH client? I am running 386.2_6 on an RT-AX88U & RT-AX58U, connected from Windows 10 desktop, via PowerShell tabs in Terminal, sessions never drop unless I close them myself.

 

[lhoekenga]

I'm using the command line ssh client from MacOS, which I use all day for work. I'll see if I get different results from my windows box. Thanks for the suggestion!

 

[lhoekenga]

@archiel looks like it is the ssh client on MacOS Big Sur. I've tried PuTTY on my windows box and it's appears to be working w/o dropping. Thank you for the suggestion.

 

[lhoekenga]

I did find the solution in this thread
Ssh connection to router gets reset every few seconds

It's a combination of dropbear's "-k" option and having set ServerAliveInterval in .ssh/config. I can't remember why I would have had that option set, so I removed it, and ssh to my router is working great.