Packet loss in virtualized OpenWRT over Proxmox

Installing and Using OpenWrt
1

Hello,

I’ve set up a virtualized OpenWrt router inside a Proxmox environment.
The goal is to route traffic between a “normal” LAN (no VLAN support on the main router)
and a VLAN-based internal network handled by OpenWrt.

Topology is shown in the diagram below.

image
image875×592 22 KB

However, I’m experiencing a persistent issue with SSH connections (at least)
only from Windows hosts.

Symptoms:

  • SSH connection establishes correctly
  • After some time, the connection freezes and then drops
  • tcpdump shows that OpenWrt and the SSH server keep sending packets
  • Windows client stops ACKing some packets even though they are received
  • No firewall drops are logged
  • Disabling the OpenWrt firewall does NOT fix the issue
  • Offloading (GRO/GSO/TSO) disabled on Proxmox and OpenWrt
  • rp_filter disabled
  • MSS clamping tested (both clamp-to-PMTU and fixed MSS)
  • Same behavior with multiple Windows hosts
  • SSH from Proxmox host works fine and stays stable

Has anyone seen similar behavior when running OpenWrt virtualized? Any ideas where to look next?

Thanks for your help!

2

To be clear, what SSH client are you running?

3

Hi,

I've try Power shell (with SSH command), Putty and doing SSH behind an WSL, and all of them have the same problem.