by Adam Armstrong

Dell Mellanox ConnectX-4 Lx Dual Port 25GbE DA/SFP rNDC NIC Review

The Dell Mellanox ConnectX-4 Lx is a dual port network interface card (NIC) designed to deliver high bandwidth and low latency with its 25GbE transfer rate. What is interesting about this NIC is that it is designed specifically for the Dell PowerEdge line of servers (specifically the R630, R730, R730xd, and R930), slotting into the motherboard without taking up a traditional PCIe slot. The Dell Mellanox ConnectX-4 Lx aims to bring about all of the performance promise of the PowerEdge servers while not letting networking be the bottleneck that slows everything down.

The NIC works with both 10 and 25GbE environments, making it a good choice as an organization is upgrading its backend networking fabric to a next-gen hardware. The NIC also supports RDMA over Converged Ethernet, Ethernet stateless offload engines, Overlay Networks, and GPUDirect Technology making it a good choice for several use cases including Web 2.0, Cloud, data analytics, database, and storage platforms. Data centers using the NIC can see better server utilization as it can isolate and protect VMs within the server through I/O virtualization.

A single NIC can appear as multiple virtual NIC’s, reducing CAPEX through the utilization for LAN and SAN unification. The NIC can also lower CPU overhead to further lower OPEX and CAPEX.

Dell Mellanox ConnectX-4 specifications:

  • Device Type: Network Adaptor
  • Form Factor: Plug-in card (rNDC)
  • Interface: PCIe
  • Networking
    • Ports: 25 Gigabit Ethernet x 2
    • Connectivity Technology: Wired
    • Data Link Protocol: 25 Gigabit LAN
    • Data Transfer Rate: 25Gbps
  • Expansion / Connectivity
    • Interfaces: 2 x 25Gb Ethernet
  • Designed For: Dell PowerEdge R630, R730, R730xd, R930

Design and Build

The Dell Mellanox ConnectX-4 Lx is "no" profile, dual Ethernet configuration, plug in network interface card. The card is easy to install inside a compatible Dell PowerEdge server. Users unscrew the existing rNDC card in the rear of the server (often populated with the default quad 1GbE interface), push the replacement card in, and you are ready to configure it and go.

Installation generally requires no tools, but the set screws if too tight to undo manually need only a Phillips head screwdriver to loosen or tighten.


Designed specifically for Dell PowerEdge Servers, the Dell Mellanox ConnectX-4 Lx offers high bandwidth and low latency, all without taking away a single PCIe slot from other add-on devices. The NIC supports RDMA over Converged Ethernet, Ethernet stateless offload engines, Overlay Networks, and GPUDirect Technology making it an ideal choice for several different use cases. Furthermore, the NIC can reduce CAPEX and OPEX through LAN and SAN unification, and can lower CPU overhead giving the data center better server utilization in general.

In the coming weeks StorageReview will be migrating over to a new 25/50/100Gb networking backend, where these NICs will play a key role in upgrading our existing Dell PowerEdge R730 servers to support the faster networking fabric. The rNDC cards specifically are quite valuable to us, taking up no additional space in our Dell servers, leaving all 7 PCIe slots open for other hardware add-ons. 

The Bottom Line

The ConnectX-4 Lx Dual Port 25GbE rNDC NIC is designed to integrate seamlessly into Dell EMC PowerEdge servers, without taking away expansion room for other devices.

Dell Mellanox ConnectX-4 product page

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