What This Port Is
Port 348 is officially assigned to csi-sgwp (Cabletron Management Protocol) for both TCP and UDP. The assignment belongs to Cabletron Systems, Inc., a networking equipment manufacturer that dominated parts of the Ethernet market in the 1980s and 1990s.
The protocol was used for managing Cabletron's networking equipment—switches, hubs, and routers that once filled data centers across America.
The company no longer exists. The equipment is long retired. But the port assignment remains.
The Well-Known Ports Range
Port 348 falls within the well-known ports range (0-1023)—also called System Ports. These ports are assigned by IANA through formal procedures like "IETF Review" or "IESG Approval."1
Well-known ports require elevated privileges to bind on Unix-like systems. They're meant for standardized services that the entire Internet might depend on. Port 348 technically qualifies, but nobody depends on it anymore.
It's a reserved seat at a table where the guest never shows up.
The Story: Cabletron Systems
Cabletron Systems was founded in 1983 in a Massachusetts garage by Craig Benson (who later became New Hampshire's governor) and Robert Levine.2 They built networking equipment during the era when Ethernet was becoming the standard for local area networks.
Their breakthrough product was the MMAC-8, one of the first modular Ethernet hubs. By developing high-density 10BASE-T modules and a management system called Prism, Cabletron made enterprise networking equipment that was actually manageable.3
Throughout the 1990s, Cabletron was a major player—significant enough to get an official IANA port assignment for their management protocol. Port 348 was their number.
In 2000, Cabletron reorganized as a holding company controlling four networking firms, including Enterasys Networks. The original Cabletron eventually merged with Enterasys before going public in 2001. The company fragmented, was acquired, and effectively disappeared.4
But port 348 stayed in the registry. IANA doesn't revoke port assignments when companies die.
Current Reality
Port 348 is officially assigned but effectively unused. The protocol it was assigned for doesn't exist in any meaningful way. No modern software expects to find Cabletron management services on port 348.
Some security databases flag port 348 as potentially associated with malware or trojans—not because the Cabletron protocol was malicious, but because attackers sometimes repurpose abandoned ports.5 An assigned-but-unused port is useful cover for malicious traffic.
If you find something listening on port 348 in 2026, it's probably not a Cabletron device.
How to Check What's Listening
To see if anything is listening on port 348 on your system:
Linux/Mac:
Windows:
If something is listening, investigate what process owns it. It shouldn't be there unless you're running very old networking equipment or something is misusing the port.
Why This Port Matters
Port 348 is a memorial. It proves that the Internet remembers better than we do.
When a company gets a port assignment, that assignment is effectively permanent. The IANA registry is designed for stability—removing assignments would break compatibility with old systems that might still be running somewhere. So ports outlive the companies that requested them.
Cabletron Systems is gone. Their equipment is in landfills. Their engineers moved on to other companies decades ago. But port 348 remains reserved, waiting for traffic that will never come.
This is true for hundreds of ports in the well-known range. They're fossils—assigned to companies and protocols that no longer exist, preserved in the registry because removing them is harder than leaving them alone.
Port 348 is a reminder that infrastructure is forever, even when what it was built for isn't.
Related Ports
Other ports in the well-known range assigned to defunct or obscure protocols:
- Port 347: Fatmen Server (CERN file system - defunct)
- Port 349: Mftp (Multisource File Transfer Protocol)
- Port 350-352: Various experimental protocols
- Port 371: Clearcase (version control system, largely obsolete)
The low-numbered ports are full of these ghosts—services that mattered enough to get an assignment but not enough to survive.
Frequently Asked Questions
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