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// DevOps, cloud & containers

Port 3121: The pacemaker remote (pcmk-remote) service extends high availability functionality outside of the Linux cluster into remote nodes.

Port 3121 is assigned by IANA to pcmk-remote (The pacemaker remote (pcmk-remote) service extends high availability functionality outside of the Linux cluster into remote nodes.).

3121

How pcmk-remote works

DevOps, cloud & containers
adminhostpcmk-remote adminhostpcmk-remote

Commands sent to port 3121 create and control containers or cluster resources on the host.

Transport
TCP
Exposure risk
not rated depends on the program listening
Encryption
Unknownnot stated by the registry
IANA status
Assigned1 registered service
Range
Registered (1024-49151)
Category
DevOps, cloud & containers
01 Security

Is port 3121 dangerous?

We have no specific security note for port 3121. Its risk depends on the program actually listening on it. General advice for devops, cloud & containers services:

  • Container and orchestration APIs give full control of hosts: require mutual TLS and RBAC.
  • Never expose them to the Internet.
  • Rotate tokens and certificates and audit who has access.
02 Registry

IANA registry entries for port 3121

ServicePortTransportDescriptionReferenceUpdated
pcmk-remote 3121 TCP The pacemaker remote (pcmk-remote) service extends high availability functionality outside of the Linux cluster into remote nodes. - 2013-03-15
-3121-Reserved--

// source: IANA service name and port number registry

03 Check it

Which program uses port 3121, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3121'      # process listening on 3121
sudo lsof -nP -i :3121

macOS

sudo lsof -nP -i :3121

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3121 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3121
netstat -ano | findstr :3121

From another machine

nmap -p 3121 -sV <host>
nc -zv <host> 3121

Block it in the firewall

sudo ufw deny 3121/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3121" -Direction Inbound -LocalPort 3121 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3121 used for?

Port 3121 is assigned by IANA to pcmk-remote (The pacemaker remote (pcmk-remote) service extends high availability functionality outside of the Linux cluster into remote nodes.).

Is port 3121 TCP or UDP?

Port 3121 is registered for TCP.

Is it safe to open port 3121?

It depends on the program that listens on it. Open it only for a service you know and only to the networks that need it. Container and orchestration APIs give full control of hosts: require mutual TLS and RBAC.

How do I check if port 3121 is open?

On Linux run "ss -ltnup 'sport = :3121'", on macOS "lsof -nP -i :3121", and on Windows "netstat -ano | findstr :3121" to see the local process. From another machine, "nmap -p 3121 <host>" shows whether it is reachable.

05 Related
:2375 Docker API (HTTP) tcp · critical risk :2376 Docker API (TLS) tcp · high risk :6443 Kubernetes API tcp · udp · high risk :10250 Kubelet API tcp · critical risk :2379 etcd tcp · critical risk :8500 Consul tcp · udp · high risk :4505 SaltStack tcp · critical risk :9000 PHP-FPM / SonarQube / Portainer tcp · udp · high risk

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