question

sajjadali-2433 avatar image
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sajjadali-2433 asked SaiKishor-MSFT commented

Azure Loadbancer can't reach from the backend VM

we have a client who has a standard load balancer, frontend ip , health probe , 2 Vms in the backend pool, and a health probe.

The load balancer is configured correctly.

if the user access the load balancer from another VM then it correctly load the page from the backend VM.

But if the user access the load balancer from one of the backend VM then its not reachable. e.g below:



  1. backendVM1# traceroute -T -p 0 10.10.10.11 (load balancer ip)

1
2

3
.....
30



  1. backendVM1# curl -v http://10.10.10.11:80/index.html

  • Trying 10.10.10.11...

  • TCP_NODELAY set

what can we do to solve this issue?

Thanks




azure-load-balancer
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1 Answer

SaiKishor-MSFT avatar image
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SaiKishor-MSFT answered SaiKishor-MSFT commented

@sajjadali-2433 Connecting to Load Balancer frontend from the participating Load Balancer backend Pool VM is not supported. This may work if the flow is not mapped to the originating VM and failures can occur if flow is mapped to the originating VM. Please find more details regarding this in this document here.

"A side effect is that if an outbound flow from a VM in the back-end pool attempts a flow to front end of the internal Load Balancer in its pool and is mapped back to itself, the two legs of the flow don't match. Because they don't match, the flow fails. The flow succeeds if the flow didn't map back to the same VM in the back-end pool that created the flow to the front end."

A resolution to this situation would be to use a proxy such as Application Gateway or other proxies such as nginx or haproxy. Hope this helps.

Please let us know if you have any further questions and we will be glad to assist you further. Thank you!

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