A converged network adapter (CNA) is a server network card that carries regular Ethernet traffic and storage traffic over one high-speed port. It combines the jobs of a network interface card (NIC) and a Fibre Channel host bus adapter (HBA), usually by running Fibre Channel over Ethernet (FCoE) on 10 Gigabit Ethernet or faster.
Key takeaways
- A CNA replaces separate NIC and HBA cards, so one adapter and one cable can serve both the LAN and the storage network.
- Most CNAs use FCoE, which wraps Fibre Channel frames inside Ethernet frames.
- FCoE needs lossless Ethernet, so the switches must support Data Center Bridging (DCB).
- CNAs cut cabling, ports and power draw, but they add switch and configuration requirements.
- Newer designs often choose iSCSI, NVMe over Fabrics or native Fibre Channel instead, so check your storage array before buying.
What does a converged network adapter do?
A converged network adapter sends two kinds of traffic through the same physical port: normal LAN traffic such as application and management data, and block-storage traffic to a SAN. Instead of installing a NIC for Ethernet and an HBA for Fibre Channel, the server uses one CNA with one or two ports. The operating system or hypervisor typically sees both an Ethernet interface and a storage adapter.
This matters most in dense server racks and virtualization hosts, where every extra card, cable and switch port adds cost, heat and cabling work. If you manage virtual machines, our guide to raw device mapping in VMware shows how those hosts present SAN storage to guests.
How does a CNA work?
A CNA works by placing Fibre Channel frames inside Ethernet frames, a method called Fibre Channel over Ethernet (FCoE). The adapter sends LAN and FCoE traffic over the same 10 GbE link to an FCoE-capable switch, and the switch splits the traffic: Ethernet frames go to the LAN, and storage frames go to the Fibre Channel SAN.
Storage traffic cannot tolerate dropped frames the way ordinary TCP traffic can, so FCoE runs on a lossless Ethernet fabric built with Data Center Bridging (DCB). DCB is a set of IEEE standards:
- Priority Flow Control (PFC, 802.1Qbb) pauses a single traffic class so storage frames are not dropped.
- Enhanced Transmission Selection (ETS, 802.1Qaz) reserves bandwidth for each traffic class.
- DCBX lets the adapter and switch agree on these settings automatically.
The FCoE Initialization Protocol (FIP) handles discovery and login, so the CNA can find the Fibre Channel fabric the same way a native HBA would. FCoE is a Layer 2 protocol, so it is not routed across IP networks like normal traffic, and its frames are larger than a standard 1,500-byte Ethernet frame, so the network must support them.
CNA vs NIC vs HBA: what is the difference?
A NIC handles only Ethernet traffic, an HBA handles only Fibre Channel storage traffic, and a CNA handles both on a single adapter. The table shows where each one fits.
| Adapter | Traffic it carries | Typical link | Best for |
|---|---|---|---|
| NIC | Ethernet (LAN and IP traffic) | 1, 10, 25 GbE and faster | General servers and workstations |
| HBA | Fibre Channel storage only | Native Fibre Channel | Servers on a dedicated Fibre Channel SAN |
| CNA | Ethernet plus FCoE (some also offload iSCSI) | 10 GbE or faster | Dense racks and virtualization hosts that need LAN and SAN access |
What are the benefits of a CNA?
The main benefit of a converged network adapter is consolidation: fewer adapters, cables and switch ports to buy, power and manage. Typical gains include:
- Less cabling. One or two links per server instead of separate LAN and SAN cables.
- Lower power and cooling. Fewer cards and ports in each server and switch.
- Simpler racks. Fewer cables make airflow and troubleshooting easier.
- Flexible bandwidth. ETS lets LAN and storage traffic share one link, with bandwidth divided by policy.
- Keeps your existing SAN. FCoE lets servers reach a Fibre Channel SAN without a full storage redesign.
Consolidation also helps when you plan a hardware refresh or a move. Our data center migration checklist covers the cabling and port audits that go with it.
What are the drawbacks of a CNA?
The drawbacks of a CNA are extra network requirements and a shared-link risk. A CNA only delivers its benefits when the whole path supports it. Watch for these issues:
- Switch support. You need switches with DCB and FCoE support, which usually cost more than basic Ethernet switches.
- Configuration complexity. PFC, ETS, VLANs and FIP must all be set correctly, and mistakes can cause storage timeouts.
- Shared failure domain. A problem on the converged link can affect both LAN and storage access, so redundant links matter. Our guide to high availability explains how to design for that.
- Shrinking ecosystem. Many newer designs choose other storage protocols, covered below.
What do you need to deploy a CNA?
To deploy a converged network adapter you need a compatible server slot, an FCoE-capable switch path, supported cabling and a storage array that offers a Fibre Channel or FCoE target. Use this checklist:
- Confirm the adapter, driver and firmware are on the hardware compatibility list of your operating system or hypervisor.
- Use 10 GbE or faster links with supported SFP+ or SFP28 optics or direct-attach cables.
- Enable DCB (PFC, ETS and DCBX) on the switch ports and set a dedicated VLAN for FCoE.
- Zone the storage fabric and map the LUNs to the CNA in the server.
- Test failover by pulling one link at a time before going live.
Storage design still matters after the link is up. Your RAID choice affects performance and fault tolerance on the array side, as covered in our RAID 50 explainer, and tools such as hierarchical storage management decide where data lives over time.
Is a converged network adapter still relevant today?
CNAs are still supported by many switches, storage arrays and hypervisors, and they remain useful where a Fibre Channel SAN already exists. However, many new data center designs choose iSCSI over standard Ethernet, NVMe over Fabrics or native 32G and 64G Fibre Channel instead of FCoE. If you are buying new storage, check which protocols the array vendor recommends before you standardize on CNAs.
Frequently asked questions
What does CNA stand for in networking?
In networking, CNA stands for converged network adapter. It is a card that combines the functions of an Ethernet NIC and a Fibre Channel HBA. It is unrelated to other uses of the acronym, such as certified nursing assistant.
What is the difference between a CNA and a NIC?
A NIC carries only Ethernet traffic. A CNA carries Ethernet and storage traffic, usually FCoE, and may offload storage protocols in hardware. Both plug into the same kind of server slot, but a CNA needs DCB-capable switches to run FCoE.
Does a CNA require FCoE?
Most CNAs are built around FCoE, but many also work as plain Ethernet adapters and some offload iSCSI. You can run a CNA as a normal 10 GbE NIC if you do not use FCoE, although a standard NIC is usually cheaper for that job.
Can a CNA work with a regular switch?
A CNA can pass ordinary Ethernet traffic through a regular switch, but FCoE needs a switch with DCB and FCoE support. Without lossless Ethernet, storage frames can be dropped, which causes timeouts and disk errors.
Are converged network adapters still used?
Yes, mainly in environments with an existing Fibre Channel SAN or an FCoE-based design. New builds often choose iSCSI, NVMe over Fabrics or native Fibre Channel instead, so check your storage vendor guidance.
Conclusion
A converged network adapter lets one port carry both LAN and storage traffic, which reduces cabling and hardware in the rack. It works best when your switches support DCB and FCoE and when you already have a Fibre Channel SAN to connect to. Before you buy, compare it with iSCSI and NVMe over Fabrics, and plan redundant links so one failure does not take down both networks. For related reading, see our guides on network collisions and virtual desktop infrastructure.
