Network ACL Configuration Examples

This section provides examples for configuring network ACLs.

Denying Access from a Specific Port
Allowing Access from Specific Ports and Protocols

Denying Access from a Specific Port

You might want to block TCP port 445 to protect against the WannaCry ransomware attacks. You can add a network ACL rule to deny all incoming traffic from TCP port 445.

Network ACL Configuration

Table 1 lists the inbound rules required.

**Table 1** Network ACL rules
Direction	Action	Protocol	Source	Source Port Range	Destination	Destination Port Range	Description
Inbound	Deny	TCP	0.0.0.0/0	1-65535	0.0.0.0/0	445	Denies inbound traffic from any IP address through TCP port 445.
Inbound	Allow	All	0.0.0.0/0	1-65535	0.0.0.0/0	All	Allows all inbound traffic.

By default, a network ACL denies all inbound traffic. You can add a rule to allow all inbound traffic if necessary.
If you want a deny rule to be matched first, insert the deny rule above the allow rule. For details, see Changing the Sequence of a Network ACL Rule.

Allowing Access from Specific Ports and Protocols

In this example, an ECS in a subnet is used as the web server, and you need to allow inbound traffic from HTTP port 80 and HTTPS port 443 and allow all outbound traffic. You need to configure both the network ACL rules and security group rules to allow the traffic.

Network ACL Configuration

Table 2 lists the inbound and outbound rules required.

**Table 2** Network ACL rules
Direction	Action	Protocol	Source	Source Port Range	Destination	Destination Port Range	Description
Inbound	Allow	TCP	0.0.0.0/0	1-65535	0.0.0.0/0	80	Allows inbound HTTP traffic from any IP address to ECSs in the subnet through port 80.
Inbound	Allow	TCP	0.0.0.0/0	1-65535	0.0.0.0/0	443	Allows inbound HTTPS traffic from any IP address to ECSs in the subnet through port 443.
Outbound	Allow	All	0.0.0.0/0	All	0.0.0.0/0	All	Allows all outbound traffic from the subnet.

Security group configuration

Table 3 lists the inbound and outbound security group rules required.

**Table 3** Security group rules
Direction	Protocol/Application	Port	Source/Destination	Description
Inbound	TCP	80	Source: 0.0.0.0/0	Allows inbound HTTP traffic from any IP address to ECSs associated with the security group through port 80.
Inbound	TCP	443	Source: 0.0.0.0/0	Allows inbound HTTPS traffic from any IP address to ECSs associated with the security group through port 443.
Outbound	All	All	Destination: 0.0.0.0/0	Allows all outbound traffic from the security group.

A network ACL adds an additional layer of security. Even if the security group rules allow more traffic than that actually required, the network ACL rules allow only access from HTTP port 80 and HTTPS port 443 and deny other inbound traffic.

Parent topic: Network ACL

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