Port 3343Windows Failover Clustering

Intra-cluster communication for Microsoft Windows Server Failover Clustering nodes.

transport: tcp · udp
in transit: cleartext
assignment: official
risk: 6/10
lookups: 0

also known as ms-cluster-net, Microsoft Cluster Service, MSCS, WSFC

Technical Details

what runs on :3343

Windows Failover Clustering registers port 3343 for cluster-service communication over both TCP and UDP; UDP is commonly associated with cluster heartbeat and membership traffic. It is an internal node-to-node protocol rather than a general-purpose client service, and deployments also use RPC endpoint mapping on TCP 135, dynamic RPC ports, and SMB on TCP 445 for related operations. Exact message formats and transport usage vary across Windows Server releases and cluster configurations.

Security Information

exposure of :3343

risk score

6/ 10risk

treat as sensitive. widely scanned and regularly exploited when reachable — restrict it to known sources.

network services averages 3.8 across 639 ports — this one sits 2.2 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

Port 3343 should be restricted to the cluster nodes and authorized management networks, never exposed directly to the public internet. An exposed service can be fingerprinted and targeted for spoofed, malformed, or resource-exhaustion traffic; compromise or disruption of cluster communications could affect highly available workloads. The port is not a substitute for the authentication and authorization controls protecting the Windows cluster itself.

Record

iana registry entry

port: :3343
service: Windows Failover Clustering
transport: TCPUDP
encryption: cleartext
assignment: iana registered
risk: 6/10risk
category: Network Services System
usage: Port 3343 is used by the Microsoft Cluster Service, now called Windows Server Failover Clustering, for node-to-node cluster communication and membership or heartbeat traffic. Engineers normally encounter it only between cluster nodes on a private or tightly restricted network, alongside RPC and SMB traffic used by cluster management and resource operations.
lookups: 0rank 994
added: 2026-08-21
updated: 2026-08-21
references: IANA service name registry — port 3343

Something wrong?

This record is maintained by the engineers who use port 3343. 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 2026-08-21.

01edit any field on a page of its own
02a model checks it for accuracy and spam
03clean and confident goes live immediately

edit this record →back to the registry

Related Ports

all 639 in network services →

the 8 most looked-up other ports in network services — 639 ports carry that label.

port	service	proto	category	risk	views
:9080	Groove RPC	TCPUDP	Web Services	caution	70.8k
:6543	Jetnet	UDP	Network Services	caution	65.3k
:5938	TeamViewer	TCPUDP	Remote Access	caution	65.0k
:8291	Winbox MikroTik Admin	TCP	Security	caution	62.9k
:3233	WhiskerControl Protocol	TCPUDP	Network Services	caution	61.9k
:3268	Microsoft Global Catalog (GC)	TCPUDP	Security	caution	54.6k
:135	Microsoft EPMAP	TCPUDP	Security	caution	51.9k
:3128	Tatsoft Default HTTP Proxy	TCP	Web Services	caution	46.8k

risk mix of the 8 listed

caution100%

0 of 8 encrypted

Port :3343Windows Failover Clustering

Technical Details

Security Information

Related Ports

Port 3343Windows Failover Clustering