Port 915 is where data center networks talk to themselves about their own structure.
What Runs on Port 915
Port 915 (UDP) carries RIFT-TIES—Routing in Fat Trees Topology Information Elements. This is the protocol that allows switches in modern data centers to automatically discover how they're connected and route traffic intelligently through fat-tree network topologies.1
The TCP version of port 915 is reserved but unassigned.
The Problem RIFT Solves
Modern data centers are built using "fat tree" topologies—networks that look like trees turned upside down. Instead of branching out toward the leaves, they branch upward toward the spine. These Clos networks have multiple paths between any two points, massive scale (thousands of switches), and regular, predictable structure.
Traditional routing protocols weren't designed for this. BGP requires too much configuration. OSPF floods too much state. IS-IS wasn't built for the directionality of fat trees. Data center operators needed something purpose-built.
RIFT is that protocol. It knows about levels (leaf, spine, super-spine). It floods topology information northbound and default routes southbound. It understands that fat trees have directionality—traffic mostly flows up and down, not sideways.
How RIFT Works
RIFT uses a hybrid approach: "link-state toward the spine, distance-vector toward the leaves."2
Here's what that means in practice:
Northbound flooding: Each switch sends its link-state information upward. The spine switches learn the complete topology of everything below them.
Southbound summarization: Spine switches send default routes downward. Leaf switches don't need to know the entire data center topology—they just need to know "send it up."
Zero Touch Provisioning: RIFT switches can discover their own level in the topology automatically. Plug in a new switch, and it figures out where it belongs by listening to its neighbors on port 915.
Topology Information Elements (TIEs): These are the UDP packets on port 915 that carry link-state information, node capabilities, prefix advertisements, and topology state. TIEs flow northbound through the fabric, building a map of connectivity as they go.
The protocol minimizes state at each level. A leaf switch doesn't need to hold routing information for 10,000 servers—it just needs to know its local connections and a default route. The spine holds more. The super-spine holds the most. The topology naturally mirrors the information distribution.
The History
RIFT was developed by the IETF Routing in Fat Trees (RIFT) working group to address the specific needs of modern IP fabrics. The protocol was standardized in RFC 9692, published in April 2025.3
Port 915 (UDP) was officially assigned to RIFT-TIES by IANA on February 17, 2023, with the assignment modified on June 7, 2024.4
Unlike protocols designed decades ago for the Internet backbone, RIFT was born in the data center era. It assumes regular topology, massive scale, and automated deployment. It's designed for networks where humans don't want to configure thousands of devices individually.
Why UDP?
RIFT uses UDP for its topology information exchange because:
- Speed matters — Topology changes need to propagate quickly through the fabric
- Multicast-friendly — RIFT can send TIEs to multiple neighbors simultaneously
- Lightweight — No connection overhead for frequent small topology updates
- Loss handling — RIFT implements its own reliability mechanisms on top of UDP, tailored to the specific needs of topology flooding
The protocol handles packet loss, reordering, and retransmission at the application layer, giving it precise control over how topology information propagates.
Real-World Use
RIFT is deployed in hyperscale data centers and IP fabrics where:
- Networks scale to thousands of switches
- Topology is regular and predictable (Clos, fat-tree variants)
- Zero-touch provisioning is required
- Operators want minimal configuration complexity
- Fast convergence on topology changes is critical
When you stream a video from a cloud service, or access files from distributed storage, or run a search query that touches hundreds of servers—there's a good chance RIFT TIEs on port 915 helped those packets find their way through the data center fabric.
Security Considerations
RIFT TIEs carry sensitive topology information. An attacker who can inject packets on port 915 could:
- Poison routing tables with false topology information
- Cause traffic to be misrouted or black-holed
- Create routing loops or suboptimal paths
- Map the internal structure of the data center network
Production deployments should:
- Restrict port 915 to trusted network segments (data center fabric only)
- Use authentication mechanisms defined in the RIFT specification
- Monitor for unexpected TIE advertisements
- Implement access controls on management interfaces
RIFT includes provisions for detecting common miscabling scenarios, but deliberate attacks require additional security measures.
Related Ports
- Port 179 — BGP (often used in traditional data center routing)
- Port 520 — RIP (older distance-vector protocol)
- Port 521 — RIPng (IPv6 version)
How to Check What's Listening
On Linux:
On macOS:
On Windows:
If you see something listening on port 915, it's likely a RIFT-enabled switch or router in a data center fabric environment.
The Bigger Picture
Port 915 represents a shift in how we think about routing protocols. Instead of adapting old protocols designed for the Internet to work in data centers, RIFT was purpose-built for the specific topology, scale, and operational requirements of modern IP fabrics.
Fat trees solve a fundamental problem: how do you connect thousands of servers with maximum bandwidth and minimal cost? The answer is regular topology with lots of cheap switches instead of a few expensive ones.
RIFT solves the next problem: how do you route traffic through that topology without drowning in configuration complexity or routing state?
Port 915 is where those two solutions meet. Every TIE packet carries a piece of the map. Every switch listening on port 915 learns a little more about the shape of the network it belongs to. And somehow, out of thousands of independent devices exchanging UDP packets, a coherent routing fabric emerges.
The data center learns its own shape. Port 915 is how it talks to itself.
Frequently Asked Questions About Port 915
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