Blocked Ports

Blocked Ports

Blocked by default (Mail)

The following ports are blocked by default to prevent spamming:

  • TCP/25 (SMTP, egress only)
  • TCP/465 (SMTPS, egress only)
  • TCP/587 (SMTPS, egress only)

To remove these restrictions, please contact our support team. Please note that we have zero tolerance for unsolicited emails and spamming and will terminate your service immediately if we receive any verified complaints.

Blocked by default (Cogent IP)

As Cogent has a very strict policy on IP address usage, the following outgoing ports are strictly rate limited by default:

  • TCP/22 (SSH)
  • TCP/23 (Telnet)
  • TCP/445 (SMB)
  • TCP/1433 (MSSQL)
  • TCP/3306 (MySQL)
  • TCP/3389 (RDP)
  • TCP/5900 (VNC)

Once your billing information is verified and agree to pay fine if any abuse is detected, we can remove these restrictions. Please contact our support team for assistance.

The current fine is $25 per abuse report. You will only be charged if Cogent issues an AHF (Abuse Handling Fee) to us.

Permanently blocked

These ports are often used for DDoS attacks. These blocks are permanent and cannot be removed.

  • TCP & UDP 1900 (SSDP)
  • UDP 11211 (Memcached)


In the locations below you may find UDP/443 (ingress) blocked or rate limited.

Unfortunately, we continue to receive an insane amount of DDoS attacks on this port and had to block it to prevent congestion. The restrictions are done on our transit providers' routers and we can't provide any exceptions at this time.

  • Singapore
  • Hong Kong
  • Taipei
  • Tokyo