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How to add an additional Network Interface to a LoadMaster in Amazon Web Services (AWS)

By default, the LoadMaster deploys with one NIC in AWS. However, it is possible to configure the LoadMaster to handle multiple NICs in AWS. This guide covers the steps to deploy an additional NIC and assumes you already have successfully deployed a LoadMaster in AWS. If you need assistance deploying a LoadMaster in the AWS platform, please refer to the link below or contact KEMP Support.

Different instance types have limitations on how many additional NICs you can add. Please refer to the AWS link below to see what instance size supports how ever many NICs you need: 

To successfully deploy another NIC, you must also deploy a few other things in AWS:

  • An elastic IP: This is the other public IP address the LoadMaster uses for the additional NIC.
  • An additional NIC: This attaches to the EC2 instance of the LoadMaster.
  • An additional Subnet in your Virtual Private Cloud (VPC): This subnet is the network of eth1.

Create an Elastic IP


Inside the AWS EC2 dashboard, go to Network & Security > Elastic IPs, then click Allocate new address at the top.


Click Allocate and then click close on the next menu. When you go back to the Network & Security > Elastic IPs tab you will see the new elastic IP. 

We will return to this later after we create the subnet and NIC.


Create an Additional Subnet

You will need to go the the VPC dashboard within AWS.  This is under services tab within 'Network and Content Delivery' section.


Inside the AWS VPC dashboard, go to Subnets


Once there you will see your subnets. Some of these might be ones already assigned to your AWS LoadMasters. Click Create Subnet at the top.


Here we can create a new subnet. Name it, select the VPC, the Availability Zone and the IPv4 CIDR block.

Note: The availability zone must be the same one where your LoadMaster is currently deployed.

Also, write down the Subnet ID and VPC number as these will be needed later.

Now that we have our additional subnet and elastic IP, we can create the second NIC and attach it.


Create an Additional NIC


Inside the AWS EC2 dashboard, go to Network & Security > Network Interfaces then click Create Network Interface at the top.


Create a new NIC and assign the subnet you just created. Use an existing security group.

Write down the Network Interface ID - this is needed later.

Now that you have the NIC, assign it to the LoadMaster:

  1. Click the new subnet. Find the subnet by Name and Subnet ID.
  2. Click Attach at the top.
  3. Select the Instance ID of the LoadMaster.


One last thing to do in AWS is to attach the elastic IP to the NIC. Go back to EC2 dashboard within AWS and browse to the Elastic IPs tab.

  1. Click the Elasitc IP you wish to associate with the NIC.
  2. At the top, click Actions and then Associate address.
  3. Select Network interface as the Resource type and then select the correct network interface based on the Network Interface ID.
  4. Select the Private IP.
  5. Click Associate in the bottom right.


When finished, a reboot is required for the new interface to show up in the LoadMaster. Then, assign an IP address to eth1. Navigate to System Configuration > Network Setup > eth1 inside the LoadMaster Web User Interface (WUI). Assign the eth1 IP as the private IP of the NIC we created.


Now you can create Virtual Services on that network and have local servers attached to it on that network.

Note: Additional routing changes are needed on the LoadMaster if the Virtual Service lives on the newly added NIC. Setting the default gateway of the new subnet inside the Virtual Service is required to force traffic back out of the new interface instead of the interface where the global default gateway lives.