Port 573: Banyan VIP — The ghost of enterprise networks past

Port 573 is officially assigned to banyan-vip—the VINES Internetwork Protocol used by Banyan VINES, a network operating system that dominated enterprise networking in the 1980s and early 1990s.¹

The protocol is extinct. Banyan Systems collapsed. VINES networks were replaced decades ago. But port 573 remains assigned, a permanent reservation in the well-known port range for a service that will never answer again.

What Banyan VINES Was

Banyan VINES (Virtual Integrated Network Service) was a distributed network operating system first released in October 1984.² It ran on UNIX System V and was built on VIP—the VINES Internetwork Protocol—which operated similarly to Xerox Network Systems (XNS) protocols.³

VINES was genuinely innovative. It pioneered automatic address configuration—when a client booted up, it broadcast a request asking servers to suggest network addresses.⁴ This was revolutionary in an era when network configuration meant manually editing text files on every machine.

By 1998, VINES powered networks at nearly half of Fortune 1000 companies.⁵ The U.S. Marine Corps standardized on VINES for both garrison and battlefield communications. During the Gulf War in 1990-1991, Marines used VINES to run email over secure radio channels and satellite links.⁶

Port 573 carried the VIP traffic that made this possible—the low-level protocol that routed packets between VINES servers and clients across enterprise networks and war zones.

Why This Port Matters

Port 573 sits in the well-known port range (0-1023), the tier reserved for fundamental Internet services assigned by IANA. Once a port receives an assignment here, it typically stays assigned forever—even when the service dies.

This creates an interesting problem. The well-known range is finite. There are only 1,024 ports in this tier. Every assignment to a dead protocol is a slot that can't be used for something new.

Port 573 is one of many such ghosts. The protocol it was built for no longer exists. The company that created it is gone. The networks that used it were decommissioned twenty years ago. But the port number remains officially assigned to banyan-vip, frozen in time.

Current Status

Port 573 has no legitimate modern use. If you find something listening on port 573, it's either:

• Legacy equipment that was never updated (extremely rare)
• Malware using an obscure port to avoid detection⁷
• A misconfigured application accidentally bound to this port

To check what's listening on port 573:

# On Linux/Mac
sudo lsof -i :573
sudo netstat -tulpn | grep :573

# On Windows
netstat -ano | findstr :573

If you find unexpected traffic on port 573, investigate it. Nothing legitimate should be using this port in 2025.

The Archaeology of Ports

Walking through the IANA port registry is like exploring ruins. Ports assigned to protocols from companies that no longer exist, services that were replaced by better alternatives, technologies that seemed essential at the time and are now utterly forgotten.

Port 573 is one of these ruins. It was assigned when enterprise networking meant Banyan VINES, when the Marine Corps used it to send email from the battlefield, when half the Fortune 1000 depended on VIP to route their packets.

The port remains. The protocol is gone. That's how the Internet ages—in layers, with the old assignments never quite disappearing, permanent markers of technologies we've moved beyond.