After struggling for over 20 hours, I wanted to share the results of my investigation regarding very poor Internet upload erformance.

#Setup

• Proxmox Server with a Single 10GbE NIC
• OPNsense VM on Proxmox
• OPNsense uses VirtIO NICs tied to the 10GbE Linux Bridge
• upstream Gateway is a OpenWRT router with 1GbE uplink
• Zyxel XS1930 Switch connecting Proxmox Host and Gateway

#Problem Internet download speeds are fine (900Mbit/s) but upload speeds are not (5-15MBit/s instead of 50MBit/s)

#Solution Various OPNsense tunables (configured for 8 CPU cores)

• hw.ibrs_disable = 1
• net.isr.maxthreads = -1
• net.isr.bindthreads = 1
• net.isr.dispatch = deferred
• net.inet.rss.enabled = 1
• net.inet.rss.bits = 6
• kern.ipc.maxsockbuf = 16777216
• net.inet.tcp.recvbuf_max = 4194304
• net.inet.tcp.recvspace = 65536
• net.inet.tcp.sendbuf_inc = 65536
• net.inet.tcp.sendbuf_max = 4194304
• net.inet.tcp.sendspace = 65536
• net.inet.tcp.soreceive_stream = 1
• net.pf.source_nodes_hashsize = 1048576
• net.inet.tcp.mssdflt = 1240
• net.inet.tcp.abc_l_var = 52
• net.inet.tcp.minmss = 536
• kern.random.fortuna.minpoolsize = 128
• net.isr.defaultqlimit = 2048

Enabling Multiqueue in Proxmox for the VirtIO NICs

(binary stepping, 1 Queue for 2 cores, 2 Queues for 4 cores, 3 Queue for 8 cores ect, total amount of all Queues mustn’t be greater then the VMs CPU cores)

Enabling Flow Control on all involved Network devices

• Proxmox hardware NIC: ethtool -K nic0 rx on tx on
• OpenWRT lan interfnace:

uci set network.lan.txpause='1'

uci set network.lan.rxpause='1'

uci commit

reload_config

• Zyxel Switch: Port -> Port Setup

Checked all Ports

Enabling Port Buffering

Zyxel Switch: Port -> Port Buffer

Checked the Port with the Gateway

#Reason

The Main reason for this problem seems to be the down-stepping of 10Gbit traffic to 1Gbit devices. Without Flow control enabled on all involved devices, the sending rate can’t be adjusted. But without enabling Port Buffering, the Switch won’t allocate resources for adjusting the traffic flow rate for slower devices.

This Problem should only affect people who use devices with different link speeds on the same switch.