3785

IANA registers 3785/tcp as bfd-echo (“BFD Echo Protocol”), but RFC 5881 specifies BFD Echo packets on UDP destination port 3785. The available evidence does not establish what, if anything, runs over TCP port 3785 or whether it should be publicly reachable. Treat a TCP listener there as unidentified until its application is confirmed.

RFC 5881 describes single-hop BFD for checking IPv4 and IPv6 connectivity between directly connected systems. Its BFD Echo packets are routed back toward their sender by the neighboring system. The RFC also describes BFD as an operations and maintenance mechanism for network services and says it is not suitable for application-to-application failure detection across the Internet.

The RFC’s UDP protocol details do not establish TCP behavior. No host observations, deployment measurements, or malware associations were supplied. Identify any TCP listener from its process and configuration before assigning it a protocol or access policy.

Protocol

IANA assigns bfd-echo to 3785/tcp, while RFC 5881 specifies BFD Echo on UDP port 3785.

Exposure

Unknown; the evidence does not establish the intended audience or use of TCP on this port.

Security

Identify any TCP listener before allowing access; the supplied BFD Echo specification is for UDP.

Prevalence

Unknown; no scoped deployment or traffic measurement was supplied.

IANA service name

bfd-echo [Confirmed] — https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.csv

RFC reference

RFC 5881 [Confirmed] — https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.csv

BFD Echo transport

UDP destination port 3785 [Confirmed] — https://www.rfc-editor.org/rfc/rfc5881.txt

BFD purpose

Single-hop IPv4/IPv6 connectivity detection [Confirmed] — https://www.rfc-editor.org/rfc/rfc5881.txt

TCP application

Unknown [Unknown] — https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.csv