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Configure Allow IP/CIDR

How it works:

  • When a request reaches the Load Balancer, the system checks the source IP address of the request.
  • If the source IP is within an allowed CIDR range, the request is accepted and forwarded to the backend server.
  • If the source IP is not within an allowed CIDR range, the request is rejected and not forwarded.

When to configure Allow CIDRs:

  • Enhance security: Block unwanted connections to reduce the risk of external attacks.
  • Access control: Manage access to the Load Balancer by declaring a list of allowed CIDRs.
  • Performance optimisation: Reduce Load Balancer load by blocking unwanted traffic.

Configuration steps​

Step 1: Go to the Load Balancer home page on FPT Cloud Portal.

Step 2: Click the Load Balancer you want to configure.

Step 3: In the Load Balancer detail view, select the Listener tab.

Step 4: Click the Listener name you want to configure to open the Update screen.

Step 5: On the Update Listener page, in the Overview tab, find the Allow CIDRs section. Enter one or more allowed IP ranges, one per line.

Allow CIDRs and Deny CIDRs section in the Listener Overview tab

Example:

192.168.0.0/24
172.16.0.0/24

Only IP addresses belonging to these two IP ranges will have access.

Step 6: Click Update Listener in the bottom right corner to save.

note
  • Only declare trusted CIDRs to avoid abuse.
  • After changing the configuration, verify that the service is still accessible.
  • If another firewall such as FPT Cloud NGFW is placed in front of the Load Balancer, configure the corresponding rules on that firewall as well.