What Port 2174 Is
Port 2174 is officially registered with IANA as MS Firewall Intra Array, assigned to both TCP and UDP.1 It was registered in 2004 by Itai Greenberg at Microsoft for use in Microsoft ISA Server (Internet Security and Acceleration Server) and its successor, Microsoft Forefront Threat Management Gateway (TMG).
The product line is discontinued. Microsoft ended mainstream support for Forefront TMG in 2012 and extended support in 2020.2 Port 2174 remains in the IANA registry, a registered fossil.
What It Did
ISA Server and Forefront TMG could be deployed in arrays — clusters of firewall nodes that shared configuration and coordinated traffic handling. For those nodes to function as a coherent unit, they needed a dedicated internal communication channel.
Microsoft registered a family of four ports for this purpose:
| Port | Name | Purpose |
|---|---|---|
| 2171 | MS Firewall Storage | EMS to firewall sync (domain mode) |
| 2172 | MS Firewall Storage Secure | EMS to firewall sync (workgroup mode) |
| 2173 | MS Firewall Storage Replication | Primary to replica EMS replication |
| 2174 | MS Firewall Intra Array | Node-to-node array coordination |
Port 2174 was the channel between peers — the port firewall nodes used to talk directly to each other within the array, as opposed to talking to the management server.3
Who Uses This Port Today
Almost no one. Forefront TMG reached end of life over a decade ago, and Microsoft has not shipped a successor product that uses these ports. If you see traffic on port 2174 on a modern network, it warrants investigation — it is not associated with any current software.
Is This Port in the Registered Range?
Yes. Port 2174 falls in the registered port range (1024–49151). These ports are assigned by IANA upon application — any vendor or developer can request one for a specific service. Unlike well-known ports (0–1023), registered ports don't require elevated privileges to bind to, and many are associated with commercial or proprietary software rather than open standards.
The registered range contains thousands of ports like 2174: once-assigned, now-dormant registrations from products that no longer exist. IANA doesn't automatically reclaim them.
How to Check What's Listening on This Port
On Linux or macOS:
On Windows:
If anything is listening on port 2174 on a modern system, check what process owns it. It won't be ISA Server.
Frequently Asked Questions
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