Intel does not recommend to use more than one network card in a desktop board as only server system has dedicate pipes or buses to handle that kind of load, probably that is the reason of the problem. If you need a multiple ports you could try a router or switch, but if what you are looking for is a full duplex connection you could try a network card with 2 jacks for dedicated access, but need to check with your ISP (Internet Service Provider) if that is possible in your area.
Wondering what you ended up doing? I upgraded to this same board, installed 16GB RAM with I5 2400 processor. Using the same NIC's I had on the previous motherboard Intel® Desktop Board DQ35JO - which by the way never crashed. Only reason I upgraded was I needed more RAM to run 64bit Virtual Machines on ESX5. My DH67CL boots but is locking up? I've ran a cpu stress test - fine. Ran memtest86 - fine. Monitored the temp - fine. I saw this post and previous reply "NOT to have multiple NIC's installed in this board"? I'm curious why my OLD DQ35JO board ran fine with multiple NIC's for two years and this brand new DH67CL does not support multiple NIC's. Where can I validate the previous response?
Thank you for contacting the Intel Communities.
Regarding the scenario you are encountering with.
The amount of PCIe lanes that a system would be able to handle depends on the different components in the computer.
Now in order to find out which would be the issue in this case we should check the following:
Which are the PICe configurations that your Motherboard supports?
For Intel® Desktop Board DH67CL would be:
-One PCI Express 2.0 x16 add-in card connector
-Two PCI Express 2.0 x1 add-in card connectors
-Three Conventional PCI bus connectors not exceeding x16
Also, you should check with the exact model of the NIC cards used if they are able to share the bandwidth or not between the PCIe lanes.
This would also be affected by the processor.
For Intel® Core™ i5-2400 Processor
Information found in datasheet for processor page 12
Please verify the amount of lanes your NICs use and compare it with the capabilities of your system.
Some links related:
Datasheet for Motherboard: https://downloadmirror.intel.com/19488/eng/DH67CL_TechProdSpec04.pdf
Starting with the 6 Series chipset, native support for the PCI bus was dropped from the feature set. In order for boards based on 6 Series or later chipsets to provide PCI bus connectors, a (third-party) PCIe to PCI bridge IC is necessary. Unfortunately, these ICs have many compatibility issues (especially with very old PCI cards) and limitations on the throughput supported. It's likely that one of these issues is preventing your multiple NIC cards from operating...