4754
Summary
- // if you see it open
- GRE-in-UDP carries tunnel traffic and does not itself provide congestion control beyond the encapsulated traffic. RFC 8086 describes optional DTLS for GRE-UDP-DTLS on port 4755; that is distinct from the 4754 assignment.
- // common applications
- GRE-in-UDP tunnels Outer UDP destination port 4754 identifies GRE-in-UDP. The source port may carry flow entropy for ECMP. RFC 8086 specifies congestion and checksum requirements that depend on tunnel scenario and IP version.
About port 4754/udp.
UDP port 4754 is assigned to GRE-in-UDP encapsulation, a tunnel format that carries GRE packets inside UDP. The specification allows use on the general Internet under defined requirements, but the assignment alone does not establish that a host is running it or that a particular service should be publicly reachable. Permit it only where the tunnel is intentionally configured and its traffic and endpoint policies are understood.
GRE-in-UDP lets the outer UDP source port provide flow entropy, which routers can use to distribute traffic across equal-cost paths. The destination port identifies GRE-in-UDP; RFC 8086 also assigns 4755 to GRE-UDP-DTLS. GRE and UDP headers are applied and removed together at tunnel endpoints.
RFC 8086 distinguishes general Internet tunnels from tunnels in traffic-managed controlled environments. It requires congestion-controlled traffic or managed networks to avoid congestion, recommends a UDP checksum over IPv4, and requires one over IPv6 for the default tunnel. The supplied evidence does not establish prevalence, vendor implementations, or malware associations.
- Exposure
- Unknown — registry and protocol specification do not establish the intended audience of a specific deployment.
- Protocol
- GRE packets encapsulated in UDP, as specified by RFC 8086.
- Security
- Treat unexpected traffic as unverified tunnel traffic; the specification describes optional DTLS on port 4755, not 4754.
- Service
- gre-in-udp, GRE-in-UDP Encapsulation [Confirmed] — https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.csv
Protocol
GRE-in-UDP encapsulation carries network protocol packets within GRE and UDP headers
- Destination port
- RFC 8086 specifies 4754 for GRE-in-UDP and 4755 for GRE-UDP-DTLS [Confirmed] — https://www.rfc-editor.org/rfc/rfc8086.txt
- Deployment status
- Whether any particular host uses this port is Unknown [Unknown] — https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.csv
Service assignments.
| Name | Protocol | Description | Open frequency |
|---|---|---|---|
| gre-in-udp | TCP | GRE-in-UDP Encapsulation | 0.00% |
Service assignments from the IANA Service Name and Transport Protocol Port Number Registry, with open-frequency data from nmap-services.