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Troubleshooting "Http/1.1 Internal Server Error 43531" After Upgrading ADC Appliance

BY Jaber Posted August 10, 2023 Update August 14, 2023
Troubleshooting

Get solutions for 'HTTP/1.1 Internal Server Error 43531' post-ADC Appliance upgrade. Our guide simplifies troubleshooting for enhanced server uptime.



Understanding the Issue

The problem lies in the load balancing IP configurations, particularly with the non-routable load balancing VIP. In ADC 11.0-67+ builds, a design change was introduced. Now, the ADC internally probes the load balancing VIP when it is added in the Gateway session profile. This change was made to prevent crashes; however, it can lead to the "Http/1.1 Internal Server Error 43531" error under certain circumstances.

Root Cause Analysis

When the ADC attempts to probe the non-routable load balancing VIP, it needs to find the source IP for the probing process. In some cases, this source IP cannot be found, resulting in a failed probe and triggering the error message. Previous builds of the ADC did not perform this probing action, but it was introduced in ADC 11.0-67+ to enhance stability.

Solution 1: Adding an SNIP in the Same Subnet as the Load Balancing VIP

One effective solution to resolve the "Http/1.1 Internal Server Error 43531" error is to add a Subnet IP (SNIP) in the same subnet as the non-routable load balancing VIP address. By adding an SNIP, the ADC will have a valid source IP for probing the load balancing VIP during the Gateway session. Here's how you can do it:

  1. Identify the subnet in which the non-routable load balancing VIP resides.
  2. Access the ADC administration interface.
  3. Navigate to the "Network" section and select "IP" from the menu.
  4. Click on "Subnet IP Addresses" and then "Add" to create a new SNIP.
  5. Provide the required details, such as the IP address and subnet mask, ensuring that it belongs to the same subnet as the load balancing VIP.
  6. Save the changes and proceed to the next solution.

Solution 2: Adding a Route for the Load Balancing VIP Subnet

Another viable solution is to add a route on the ADC specifically for the non-routable load balancing VIP subnet. By doing so, you specify the desired Subnet IP (SNIP) or NetScaler IP (NSIP) in Gateway as the source IP for probing the load balancing VIP. Follow these steps to implement this solution:

  1. Determine the non-routable load balancing VIP subnet.
  2. Log in to the ADC administration interface.
  3. Navigate to the "System" section and choose "Network" from the menu.
  4. Select "Routes" and click on "Add" to create a new route.
  5. Enter the destination subnet, which corresponds to the non-routable load balancing VIP subnet.
  6. Specify the gateway and the desired SNIP/NSIP as the source IP.
  7. Save the changes.

Conclusion

In this guide, we have explored the "Http/1.1 Internal Server Error 43531" issue that users face after upgrading the ADC appliance to version 11.0 build 67.12. We have determined that the problem stems from the load balancing IP configurations and the design change introduced in ADC 11.0-67+ builds.

To overcome this error, we have provided two effective solutions. The first solution involves adding an SNIP in the same subnet as the non-routable load balancing VIP. The second solution requires adding a route on the ADC for the load balancing VIP subnet and specifying the desired SNIP/NSIP in Gateway as the source IP.

By following these solutions, you can successfully resolve the "Http/1.1 Internal Server Error 43531" and ensure smooth authentication through Gateway without encountering any roadblocks.