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Network Port: 11211

Network Port Reference Guide

Registered Service Name

Memcached Caching

Transport Protocol

TCP/UDP

Functional Overview

Port 11211 is used by Memcached high-performance memory object caching system.

Security Risks & Vulnerabilities

Historically exploited for massive Memcrashed UDP amplification DDoS attacks with 50,000x amplification factors. Disable UDP on port 11211 immediately.

How to audit network port status

1. Scan Open Ports: Use our Port Scanner utility to verify if this port is actively listening on your host.

2. Verify Encryption: Audit the service layer to confirm SSL/TLS is protecting transmission payload.

3. Hardening Rules: Apply the firewall instructions below to shut down unauthorized inbound ports.

UFW Firewall Rules

Allow Command

sudo ufw allow 11211/tcp

Block Command

sudo ufw deny 11211/tcp

iptables Firewall Rules

Allow Command

sudo iptables -A INPUT -p tcp --dport 11211 -j ACCEPT

Block Command

sudo iptables -A INPUT -p tcp --dport 11211 -j DROP

System & Registered Ports

Port 20Port 21Port 22Port 23Port 25Port 53Port 80Port 110Port 123Port 143Port 389Port 443Port 465Port 587Port 636Port 993Port 995Port 1433Port 1883Port 3000Port 3306Port 3389Port 5432Port 5672Port 5900Port 6379Port 8080Port 8443Port 9000Port 9200Port 11211Port 27017

Port Diagnostic Tools

Port Scanner — Scan open ports on any hostOpen Port Checker — Verify if a specific port is accessibleFirewall Rule Generator — Generate iptables / nftables rulesFirewall & VPN AI — Ask firewall configuration questions

Authoritative Standards

IANA Service Name and Transport Protocol Port Number RegistryIETF RFC 6335 — Internet Assigned Numbers Authority (IANA) Procedures for the Management of the Service Name and Transport Protocol Port Number Registry

Port assignments governed by IANA. Well-known ports (0–1023) require IANA approval per RFC 6335.