Port 3784Bidirectional Forwarding Detection (BFD)

BFD control traffic rapidly detects forwarding-path failures between network devices.

transport: tcp · udp
in transit: cleartext
assignment: official
risk: 5/10
lookups: 0

also known as bfd-control, BFD, Bidirectional Forwarding Detection

1 other service is registered on port 3784. compare all 2 →

Technical Details

what runs on :3784

BFD uses a control-session state machine with Down, Init, and Up states. Peers exchange periodically timed control packets containing negotiated transmit and receive intervals, a detection multiplier, session identifiers, and discriminator values; a session is declared failed when the expected number of packets is missed. Standard BFD control uses UDP/3784, while BFD Echo uses UDP/3785 and multihop BFD commonly uses UDP/4784. The registry assignment also lists TCP/3784, although conventional BFD implementations use UDP.

Security Information

exposure of :3784

risk score

5/ 10caution

worth attention. how exposed you are depends on configuration — don't leave it reachable from the internet without a reason.

security averages 3.8 across 227 ports — this one sits 1.2 above.

in transit

cleartext

credentials and payloads are readable by anyone on path

assignment

official

registered with iana for this service — scanners fingerprint it by number

reachable over

tcp · udp

udp is connectionless — source addresses are trivially spoofed and it is a reflection favourite

security overview

BFD is not encrypted by default. An exposed endpoint can be targeted with forged or disruptive control traffic to force sessions down or consume device resources; authentication is available in BFD implementations but is not universally enabled. BFD should normally be restricted to configured peer addresses and protected with interface, ACL, control-plane policing, and anti-spoofing controls rather than exposed to the public internet.

Record

iana registry entry

port: :3784
service: Bidirectional Forwarding Detection (BFD)
transport: TCPUDP
encryption: cleartext
assignment: iana registered
risk: 5/10caution
category: Security Network Services
usage: BFD control packets are exchanged between routers, switches, and other network devices to detect forwarding failures faster than routing-protocol timers. Standard deployments commonly use UDP port 3784 for single-hop BFD; the IANA assignment lists both TCP and UDP.
lookups: 0rank 994
added: 2026-08-25
updated: 2026-08-25
references: IANA service name registry — port 3784
RFC 5881

Something wrong?

This record is maintained by the engineers who use port 3784. Every field on it is editable — change what's wrong, say how you know, and a reviewer publishes it, usually within a minute. Last touched 2026-08-25.

01edit any field on a page of its own
02a model checks it for accuracy and spam
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edit this record →back to the registry

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risk mix of the 8 listed

caution100%

3 of 8 encrypted

Port :3784Bidirectional Forwarding Detection (BFD)

Technical Details

Security Information

Related Ports

Port 3784Bidirectional Forwarding Detection (BFD)