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Port 10257 (kube-controller-manager)

Secure metrics and health endpoint of kube-controller-manager.

Registered (user) port, 1024-49151 TCP Containers and Kubernetes Do not expose to the internet

What port 10257 is used for

Secure metrics and health endpoint of kube-controller-manager.

Security: should port 10257 be open?

Do not expose to the internet. Control-plane only; scrape it from inside the cluster.

IANA assignment

Port 10257 is in the registered range and has no IANA assignment. The usage above is unofficial but widespread.

Check what is listening on port 10257

Linux: is anything listening on TCP 10257?
sudo ss -tlnp 'sport = :10257'
Linux / macOS: which process owns the port
sudo lsof -nP -i :10257
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':10257 '
Windows (Command Prompt)
netstat -ano | findstr :10257
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 10257 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 10257
From Windows
Test-NetConnection HOST -Port 10257

Block port 10257 in the firewall

ufw
sudo ufw deny 10257/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 10257 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 10257 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 10257' -Direction Inbound -Protocol TCP -LocalPort 10257 -Action Block

Related ports

10259kube-scheduler6443Kubernetes API server10250Kubelet API10252apollo-relay10253eapol-relay10260axis-wimp-port10261tile-ml10288blocks

All port numbers · Open port checker
Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.