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Customer experience | Sales, Customer Insights,...
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Dynamics 365 Server - 500 Internal Server Error w/ Hardware Load Balancer

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Posted on by 5

Hi All,

We have an issue in our CRM environment (Dynamics 365 server v8.2.0002) whereby calls from BizTalk to the CRM organization.svc URL are occasionally failing (but consistently when under load) with the following error coming back from CRM (Verified in IIS logs):

"500 internal server error - The security context token is expired or is not valid"

Flow is as follows

BizTalk -> Barracuda Load Balancer set to Cookie Persistence mode -> CRM Servers (Three)

And back the other way.

All traffic flow is on an internal LAN.

Does anyone have any advice or previous experience with this error or are there some settings we can check or verify are correct based on best practice when using a hardware load balancer?

What has been checked so far:

- NLB is ticked on all CRM servers on the deployment wizard (Three in total)

- Persistence mode on the barracuda load balancer has been set to both none and cookie based

- Checked packet flow to ensure the load balancer isn't altering the packet or headers in any way

- Issue is occurring when hitting all three CRM servers, not isolated to a specific one

- Issue is intermittent but occurs more frequently when server is under load

- Made sure system times on all three systems are in sync. (Within the minute)

I have the same question (0)
  • Suggested answer
    Hüseyin Sahin Profile Picture
    on at

    Hello Testujay,

    we have faced this issue in the past caused by the Barracuda NLB algorithms.

    The Round Robin (algorithm) was causing intermidiate authentication errors. (Authentication not consistent)

    Our error was: At least one security token and the message could not be validated

    Which is the same scenario like you are facing as calls against MSCRM Services failed.

    Fact:

    The problem you face here is with the NLB and not the CRM Servers (I assume the CRM Servers are deployed correct). Barracuda is a 3rd party NLB causing your CRM to be unsupported as the traffic is handled by it.

    We have been in touch with Barracuda in the past and they welcome you always to raise a case with them to isolate the issue.

    Without telemetry (WireShark/Netmon/Barracuda Logs etc.) it will be challenging to find the cause.

  • Testujay Profile Picture
    5 on at

    Thanks for the reply. I appreciate it.

    We have a ticket open with Barracuda (Early days) so we'll see if they can help. The Barracuda is set to use Weighted instead of Round Robin. Did this also cause issues in your experience?

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