High RX Errors on CHR with Intel 82599ES Passthrough – Need Option to Configure RX Buffer Size

RouterOS Virtualization
1

Hi everyone,

I’m running MikroTik CHR on VMware ESXi with an Intel 82599ES 10Gbps NIC passed through via PCIe. I’m experiencing a large number of RX errors on this interface — even though the MTU is set correctly (9000) and there are no TX drops or other apparent issues.

After contacting MikroTik support, I was informed that:

RouterOS does not currently allow configuring RX buffer size, and it defaults to 128 for this NIC.

There is no way to increase or tune it, even with PCI passthrough.

Custom builds or patches are not possible due to internal resource limits.

The feature request has been forwarded, but there’s no promise of implementation.

This RX error issue causes packet drops, performance instability, and sometimes latency spikes, especially under high throughput or bursty traffic.

My Questions to the Community:

Are you also using CHR with Intel 82599ES, or any other 10Gbps NIC, and seeing similar RX errors?

Would you find it valuable if MikroTik allowed RX buffer size configuration (even under an “Advanced” or “Experimental” flag)?

Any workarounds that have helped you mitigate this?

Why this matters:

Many users (especially ISPs or hosting providers) rely on CHR for high-speed routing and firewalling. Without RX buffer tuning, we’re limited in throughput and stability — even on powerful hardware.

If others are affected too, let’s make some noise and maybe MikroTik will prioritize this in future versions.

Thanks!

2

Check IRQ settings under system/resource/irq. Ideally, you want a NIC that has enough IRQs that you can set one for each CPU core, as in “ether1” (or whatever interface you are using) should have eight entries in the table set to CPU cores 0 through 7 for an eight core CPU.