Always On VPN IKEv2 Load Balancing with F5 BIG-IP

Always On VPN IKEv2 Load Balancing with F5 BIG-IPThe Internet Key Exchange version 2 (IKEv2) is the protocol of choice for Always On VPN deployments where the highest level of security is required. Implementing Always On VPN at scale often requires multiple VPN servers to provide sufficient capacity and to provide redundancy. Commonly an Application Delivery Controller (ADC) or load balancer is configured in front of the VPN servers to provide scalability and high availability for Always On VPN.

Load Balancing IKEv2

In a recent post I described some of the unique challenges load balancing IKEv2 poses, and I demonstrated how to configure the Kemp LoadMaster load balancer to properly load balance IKEv2 VPN connections. In this post I’ll outline how to configure IKEv2 VPN load balancing on the F5 BIG-IP load balancer.

Note: This article assumes the administrator is familiar with basic F5 BIG-IP load balancer configuration, such as creating nodes, pools, virtual servers, etc.

Initial Configuration

Follow the steps below to create a virtual server on the F5 BIG-IP to load balance IKEv2 VPN connections.

Pool Configuration

To begin, create two pools on the load balancer. The first pool will be configured to use UDP port 500, and the second pool will be configured to use UDP port 4500. Each pool is configured with the VPN servers defined as the individual nodes.

Always On VPN IKEv2 Load Balancing with F5 BIG-IP

Virtual Server Configuration

Next create two virtual servers, the first configured to use UDP port 500 and the second to use UDP port 4500.

Always On VPN IKEv2 Load Balancing with F5 BIG-IP

Persistence Profile

To ensure that both IKEv2 UDP 500 and 4500 packets are delivered to the same node, follow the steps below to create and assign a Persistence Profile.

1. Expand Local Traffic > Profiles and click Persistence.
2. Click Create.
3. Enter a descriptive name for the profile in the Name field.
4. Select Source Address Affinity from the Persistence Type drop-down list.
5. Click the Custom check box.
6. Select the option to Match Across Services.
7. Click Finished.

Always On VPN IKEv2 Load Balancing with F5 BIG-IP

Assign the new persistence profile to both UDP 500 and 4500 virtual servers. Navigate to the Resources tab on each virtual server and select the new persistence profile from the Default Persistence Profile drop-down list. Be sure to do this for both virtual servers.

Always On VPN IKEv2 Load Balancing with F5 BIG-IP

Additional Resources

Windows 10 Always On VPN IKEv2 Load Balancing with Kemp LoadMaster Load Balancer 

Windows 10 Always On VPN IKEv2 Security Configuration

Windows 10 Always On VPN and IKEv2 Fragmentation

Windows 10 Always On VPN Certificate Requirements for IKEv2

Video: Windows 10 Always On VPN Load Balancing with the Kemp LoadMaster Load Balancer

Leave a comment

9 Comments

  1. Adam

     /  March 21, 2019

    Hi Richard
    How did you configure your health monitors for IKEV2?

    Reply
  2. Jimmy

     /  April 2, 2019

    Hi Richard,

    Regarding load balancing, is there anyway to load balance Always on without any appliance i.e f5, kemp etc, like using two servers running always on vpn, load balance without any appliance.

    Reply
    • Certainly. You could configure two public IP addresses (one for each VPN server) and then use DNS round robin to load balancer client requests. You could also use Windows Network Load Balancing (NLB).

      Reply
  3. Zack

     /  April 17, 2019

    Thanks for the article. When we set it up we had trouble getting clients to move from one VPN server to the other. We found a couple settings on the F5 that made a difference. By default when creating a server the type is standard (which still allows for the UDP config but didn’t connect even with port settings specified). We had to update it to Performance (Layer 4) and set the Source Address Translation to Auto Map. After that we can move back and forth between two VPN servers easily. Should be great for a DR situation.

    Reply
    • My pleasure! I didn’t go in to the low-level detailed configuration of the F5 in this article, mostly because I expect the administrator will have intimate knowledge of F5 configuration. However, I typically use Performance L4 anyway and wasn’t aware there were issues with failover. Thanks for sharing!

      Reply
  1. Always On VPN IKEv2 Features and Limitations | Richard M. Hicks Consulting, Inc.

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