Port 11211: Memcached
Memcached cache server. Exposed UDP memcached produced the largest amplification attacks on record (over 1 Tbps in 2018). Never expose it.
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Port Lookup
Port 11211 at a glance
Port11211
ProtocolTCP/UDP
ServiceMemcached
Open to the Internet?No, keep it on a private network
See What Is Listeningss -lntup | grep ':11211 '
Test From Outsidenc -zv your-server 11211
Block with UFWufw deny 11211/tcp; ufw deny 11211/udp
Block with nftablesnft add rule inet filter input meta l4proto { tcp, udp } th dport 11211 drop
Memcached uses TCP/UDP port 11211. Memcached cache server.
Exposed UDP memcached produced the largest amplification attacks on record (over 1 Tbps in 2018). Never expose it.
If ss shows something listening on port 11211 on a public address, bind it to 127.0.0.1 or a private interface in the service's own configuration, and drop the port in the firewall as well.
Other Ports
20 FTP Data21 FTP22 SSH23 Telnet25 SMTP53 DNS67 DHCP Server80 HTTP110 POP3123 NTP143 IMAP161 SNMP389 LDAP443 HTTPS445 SMB465 SMTPS514 Syslog587 Mail Submission853 DNS over TLS993 IMAPS995 POP3S1194 OpenVPN1433 Microsoft SQL Server1900 SSDP / UPnP2049 NFS2083 cPanel (SSL)2087 WHM (SSL)3306 MySQL / MariaDB3389 RDP3478 STUN / TURN5060 SIP5432 PostgreSQL5900 VNC6379 Redis8006 Proxmox VE8080 HTTP Alternate8443 HTTPS Alternate11211 Memcached25565 Minecraft27017 MongoDB51820 WireGuard
Questions
What is port 11211 used for?
Memcached. Memcached cache server.
Is it safe to open port 11211?
No, keep it on a private network. Exposed UDP memcached produced the largest amplification attacks on record (over 1 Tbps in 2018). Never expose it.
How do I check if port 11211 is open?
On the server, ss -lntup | grep ':11211 ' shows what is listening. From another machine, nc -zv your-server 11211 shows whether the firewall lets it through.
How do I block port 11211?
With UFW: ufw deny 11211/tcp and ufw deny 11211/udp. With nftables, add a drop rule for dport 11211 in your input chain.
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