Why Are Some Ports of ECSs Inaccessible?

When adding a security group rule, you must specify a port or port range for communications. Traffic is then allowed or denied if traffic matches this rule.

Table 1 lists some high-risk ports that are blocked by default. Even if you have added a security group rule to allow access over these ports, traffic over these ports in restricted regions is still denied. In this case, do not use these high-risk ports for your services.

**Table 1** High-risk ports
Protocol	Port
TCP	42, 135, 137, 138, 139, 444, 445, 593, 1025, 1068, 1433, 1434, 3127, 3128, 3129, 3130, 4444, 4789, 5554, 5800, 5900, 8998, 9995, and 9996
UDP	135 to 139, 1026, 1027, 1028, 1068, 1433, 1434, 4789, 5554, 9995, and 9996

Parent topic: Security

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