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Barracuda CloudGen Firewall

How to Add AWS Elastic Network Interfaces to a Firewall Instance

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To make traffic between subnets visible in the firewall, you must add one network interface per subnet. The number of network interfaces you can add to your instance is limited by the instance type. Firewall instances with multiple network interfaces cannot be deployed in a high availability configuration.

AWS Reference Architectures

This article is used in the following AWS reference architectures:

Before You Begin

  • Deploy a firewall instance in the public subnet of the VPC. For more information, see How to Deploy an F-Series Firewall in AWS via AWS Console.
  • Verify that the Elastic IP address is associated with the elastic network interface (ENI) of the firewall instance and not with the instance itself.
  • Stop the firewall instance. Additional network interfaces cannot be attached to a running system.

Step 1. Add an Elastic Network Interface

Create an elastic network interface. This interface will then be attached to the instance later.

  1. Log into the AWS console.
  2. Click Services and select EC2.
  3. In the Network & Services section of the left menu, click Network Interfaces.
  4. Click Create Network Interface. The Create Network Interface popover opens.
    add_eni_01.png
  5. Configure the network interface:
    • Description – Enter a description for the network interface. 
    • Subnet – Select the private subnet in the VPC for the network interface. The subnet must be in the same Availability Zone as the firewall instance.
    • Private IP – Enter a free IP address in the subnet. The first three IP addresses in the subnet are reserved by AWS.
    • Security groups – Select the security group assigned to the firewall instance.
    add_eni_02.png
  6. Click Yes, Create.

The elastic network interface is now listed with the Status column showing Available.

add_eni_03.png

Step 2. Disable Source/Destination Check

To be able to perform NAT operations, the source/destination check must be disabled.

  1. Log into the AWS console.
  2. Click Services and select EC2.
  3. In the Network & Services section of the left menu, click Network Interfaces.
  4. Right-click on the network interface created in step 1 and click Change Source/Dest. Check. The Change Source/Dest. Check popover opens.

    add_eni_04.png

  5. Select Disabled.
  6. Click Save.
    add_eni_05.png

The network interface is now able to handle traffic with destination IP addresses that do not match its own private IP address.

Step 4. Attach the Network Instance to the Firewall Instance

Verify that the firewall instance is shut down, and then add the network interface to the instance.

  1. Log into the AWS console.
  2. Click Services and select EC2.
  3. In the Network & Services section of the left menu, click Network Interfaces.
  4. Right-click on the network interface created in step 1 and click Attach. The Attach Network Interface popover opens.
    add_eni_06.png

  5. In the Instance ID list, select the firewall instance.
  6. Click Attach.
    add_eni_07.png

Step 5. Start the Firewall Instance

  1. Log into the AWS console.
  2. Click Services and select EC2.
  3. In the Instances section of the left menu, click Instances.
  4. Right-click the firewall instance, select Instance State, and click Start. Wait for the firewall instance to start.
  5. Log into the firewall.
  6. Go to CONTROL > Networking.
  7. Verify that the network interface you attached in step 4 is listed.
    add_eni_08.png

Step 6. Add the Network Interface in the Firewall Configuration

The network interface must be added and configured in the firewall configuration.

Step 6.1. Add the Network Interface
  1. Log into the firewall.
  2. Go to CONFIGURATION > Configuration Tree > Box > Network.
  3. Click Lock.
  4. In the left menu, click Interfaces.
  5. In the Network Interface Cards table, double-click the 10dynmod entry. The Network Interface Cards: 10dynmod window opens.
    add_eni_09.png
  6. From the Number of Interfaces, select the number of network interfaces attached to the firewall instance.
  7. Click OK.
    add_eni_10.png
  8. Click Send Changes and Activate
Step 6.2. Add a Direct Attached Route for the Network Interface

Add the subnet the network interface is in as a direct attached route.

  1. Go to CONFIGURATION > Configuration Tree > Box > Network.
  2. Click Lock.
  3. In the left menu, click Routing.
  4. Click + in the IPv4 Routing Table to add an attached route.
    • Target Network Address – Enter the network of the subnet in CIDR format.
    • Route Type – Select direct attached network.
    • Interface Name – Select the interface used to connect to the network. E..g, eth1
    • Trust Level –  Select Trusted.
    add_eni_11.png
  5. Click OK.
  6. Click Send Changes and Activate.
Step 6.4 Activate the Network Configuration
  1. Go to CONTROL > Box.
  2. In the Network section of the left menu, click Activate new network configuration. The Network Activation window opens.
  3. Click Failsafe.

The route is now pending in CONTROL > Network.

add_eni_12.png

Step 6.3 Add a Virtual Server IP

Add the private IP address assigned to the network interface as a virtual server IP address.

  1. Go to CONFIGURATION > Configuration Tree > Box > Virtual Servers > your virtual server > Server Properties.
  2. Click Lock
  3. Click + in the Additional IP table. The Additional IP window opens.
  4. Configure the additional virtual server IP:
    • Additional IP – Enter the private IP address configured for the network interface in step 1. 
    • Reply to Ping – Select yes.
    add_eni_13.png
  5. Click OK.
  6. Click Send Changes and Activate.

The route is now active and the virtual server IP reachable for all clients in the subnet.

add_eni_14.png

Next Steps

  • Configure the AWS route table to use the network interface as the default route for all clients in this subnet.
  • To send traffic between two subnets over the firewall, the firewall must have a network interface in each subnet. A gateway route must be added on the clients with the private IP address of the firewall used as the gateway. For more information, see AWS Reference Architecture - Segmentation Firewall for Single AZ VPCs.
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