Monitoring of high-speed networks is becoming a resource intensive task. There are dedicated flow monitoring probes built with commodity hardware support up to 10G links, but multiple 10G or even 100 G optical networks are being used for transport networks and a data center connectivity. Running and maintaining many separate probes is uneconomical and time-consuming. Therefore, we explore the possibility to facilitate network interface cards (NICs) with multiple 10G interfaces to build probes which can replace many existing boxes, leading to reduced management and operational costs. The monitoring performance is critical for such a high-density solution. We use two custom-built, FPGA-based NICs, each with eight 10G interfaces to test current CPU limits and to propose improvements for the near future commodity NICs.