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What Ports Are Blocked?

Last Updated: Mon, Mar 14, 2022
FAQ

We block several outbound ports for network security.

Blocked by default

You may request these blocks be removed by opening a support ticket.

  • TCP port 25 (SMTP)

  • TCP & UDP port 137 (NetBIOS Name Service)

  • TCP & UDP port 138 (NetBIOS Datagram)

  • TCP & UDP port 139 (NetBIOS Session)

  • TCP & UDP port 445 (SMB over TCP)

  • TCP port 1688 (Microsoft Key Management Server, inbound only)

Permanently blocked

These ports are commonly abused for DDOS attacks. These blocks are permanent and cannot be removed.

  • TCP & UDP port 17

  • TCP & UDP port 19

  • TCP & UDP port 1900

  • UDP port 53413

  • UDP port 11211

We also filter RFC1918 address ranges on public network interfaces.

  • 10.0.0.0 through 10.255.255.255 (10/8 prefix)

  • 172.16.0.0 through 172.31.255.255 (172.16/12 prefix)

  • 192.168.0.0 through 192.168.255.255 (192.168/16 prefix)

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