Delayed and/or slow SSH connection to FreshTomato router from Fedora

Ask Fedora
1

I’ll acknowledge upfront that this is question is very specific to my setup and circumstances. It is the reason I am asking it because attempting to find anything related through Google is almost impossible given the factors involved. My expectation isn’t a magic bullet answer, but rather any ideas that others may have as to what the root cause of my problem could be.

I use Fedora Workstation 42 (Gnome) on my personal laptop. I frequently use SSH to connect from Fedora to the following devices:

  1. A home lab server running a Debian Bookworm minimal install
  2. A pihole virtual machine running a Debian Bookworm minimal install
  3. A Linksys EA6700 router running the FreshTomato 2024.1 firmware configured as my local network gateway and DHCP server
  4. A Linksys EA6700 router running the FreshTomato 2024.1 firmware configured as an access point

SSH from Fedora to devices 1, 2, and 4 all work as expected. The connection occurs almost insantaneously, is stable, and is responsive. However, SSH from Fedora to device 3 is the opposite. It often takes up to 15 seconds to establish the connection. Once connected, it begins to deteriorate after a few minutes to the point of delayed inputs and eventual disconnection via timeout.

It is baffling to me because the experience is flawless when I attempt to connect to device 3 from my work laptop running Windows 10 or from device 1 after using SSH to connect to it from my personal laptop running Fedora. Furthermore, device 3 and device 4 are configured EXACTLY the same from an SSH server perspective.

My best guess right now is it has to be related to how Fedora and systemd configure the network. My network is configured for IPv4 only with IPv6 disabled on the aforementioned device 3. On my personal laptop running Fedora, I connect to it via Wi-Fi (using the wlo1 interface) letting device 3 assign the IP address and DNS servers via DHCP.

Given I have disabled IPv6 on my network, I figured doing the same on Fedora may solve the issue, but it did not. Is it possible that since it is the gateway for my network that Fedora is having a hard time connecting.

I honestly have no clue what to try next and would appreciate any and all ideas.

2

Here are some ideas to isolate the issue:

  • Connect by IP and avoid using hostnames.
  • Disable Wi-Fi power saving on the client.
  • Enable IPv6 and connect by IPv6 LLA over Wi-Fi.
  • Disable Wi-Fi on the client and connect over Ethernet.

You can also capture traffic when the issue happens and analyze the PCAP.

3

You should try again with ssh -vvv user@router for a detailed verbose output, this might give some clues as to what’s happening. Also try ssh -4 user@router to force ipv4 connection and see if this resolves the issue.

4

Thanks for the suggestions. I have not tried any of the following and will do so over the next couple of weeks:

  • Disable Wi-Fi power saving on the client.
  • Disable Wi-Fi on the client and connect over Ethernet.
5

After further testing this morning, I realized the issue isn’t specific to just Fedora. I thought it was due to selection bias. I use Fedora more than anything else for home lab administrative tasks.

The issue is reproducible from any device that connects to my router via a wireless connection. I can actually reproduce it with my access point as well if I enable wireless for it.

For anyone who may stumble across this, I am continuing my inquiry on the FreshTomato GitHub.