What Runs Here
Port 3225 is the well-known port for FCIP — Fibre Channel over TCP/IP. Defined in RFC 3821 and published in July 2004, FCIP is a tunneling protocol. It takes Fibre Channel frames — the native language of enterprise storage area networks (SANs) — encapsulates them in TCP segments, and ships them across ordinary IP networks.
IANA officially registers this port as fcip-port on both TCP and UDP.1
The Problem It Solves
Fibre Channel is the protocol that runs inside enterprise data centers for high-performance storage. It's fast, deterministic, and lossless — everything IP is not. But it has one significant limitation: distance. Fibre Channel was designed for the datacenter floor, not for connecting sites a thousand miles apart.
By the early 2000s, enterprises needed to do exactly that. Disaster recovery meant replicating storage from the primary datacenter to a remote site. Live mirroring required that both sites see the same storage fabric. The cheapest, most ubiquitous long-distance network was IP — the same one powering email and web traffic.
FCIP was the IETF's answer: wrap the Fibre Channel traffic in TCP, route it over IP, and reassemble it at the other end. The two SANs, connected by this TCP tunnel, would appear to each other as a single unified fabric.2
How It Works
When an FCIP entity wants to connect to a remote site, it opens a TCP connection to port 3225 on the remote FCIP gateway. From that point, Fibre Channel frames flow through the tunnel. The FCIP entity on the receiving end strips the TCP/IP wrapping and hands the original FC frames to the local SAN fabric.
The RFC is explicit: the FCIP entity shall listen on port 3225, though administrators can configure alternate ports if needed.3
The protocol also handles the fundamental tension between its two layers: TCP is reliable but not lossless-by-design; Fibre Channel expects exactly that. FCIP manages flow control carefully so the FC fabric above never notices it's traveling through a network that sometimes has bufferbloat.
Who Uses This Port
FCIP is enterprise infrastructure — you'll find it in large corporations and service providers running distributed datacenters, not on home networks or typical servers. Common deployments:
- Disaster recovery: Replicating storage to a geographically distant site so a fire or flood doesn't destroy the only copy
- Data center migration: Moving storage between sites without taking it offline
- Remote tape backup: Sending backup jobs to offsite tape libraries over IP
Modern NVMe-over-Fabrics and cloud object storage have changed how organizations think about distributed storage, but FCIP is still running in plenty of enterprise environments where FC SANs represent decades of investment.
Also Observed: Citrix Framehawk
The UDP range 3224–3325 (which includes port 3225) is also used by Citrix NetScaler Gateway for Framehawk, a display remoting protocol for virtual desktops. If you're seeing port 3225/UDP traffic in a Citrix environment, that's likely the cause rather than FCIP.4
What's Listening on This Port
To check what process is using port 3225 on your system:
Linux/macOS:
Windows:
On a typical workstation or server, nothing should be listening here. If something is, and you're not running Fibre Channel storage infrastructure or Citrix, investigate further.
Frequently Asked Questions
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