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Failed to add managed server: Cannot connect on-prem VBR 12.3.2 to Veeam Backup for Azure appliance (v6) over S2S VPN, same subnet on both sides, what should I do?

  • July 10, 2026
  • 3 comments
  • 41 views

Hi all, I'm stuck on this and hoping someone has faced it before.

Setup: On-prem VBR 12.3.2 (10.91.5.243). In Azure there's a Veeam Backup for Azure appliance v6 with private IP only (no public IP allowed by the customer). Connected via IPSec site-to-site VPN. I need to register the appliance in the VBR console to do a failback of an Azure VM back to on-prem vSphere.

What I've tried:

  • Add Server wizard -> Veeam cloud-native backup appliance -> connect to existing appliance, using the appliance private IP -> fails
  • Test-NetConnection to the appliance IP on 443 shows True, but I later noticed the latency is <1ms and there's an ARP entry for it on our LAN. So I think my tests were reaching some local device, not the appliance in Azure
  • Browser from the VBR server to the appliance IP gets redirected to :4343 and refused (Veeam support told me 4343 is not even a Veeam port)
  • Checked proxy on the VBR server (winhttp, IE settings, env variables). All clean, no interception
  • Veeam support confirmed v6 is compatible with VBR 12.3.2, and that the connection must come from the VBR's real IP (SNAT gets rejected)

The complication: our on-prem LAN and the appliance's Azure subnet use the same range (10.91.5.0/24) and this is intentional, so failover VMs keep their original IPs. I suspect this is why the traffic never reaches Azure: the VBR server thinks the appliance IP is on its own local network.

My question: how do people handle this? Would moving the appliance to a different subnet in the same VNET (e.g. 10.3.5.x) and routing that through the tunnel work or is there a better/proper way to connect VBR to the appliance in this kind of overlapping-subnet design? Anything I should watch out for if the appliance's IP changes?

Any advice appreciated, thanks!

3 comments

Tommy O'Shea
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  • Veeam Legend
  • July 10, 2026

Having the same subnet on both the on-prem side and Azure side is certainly what’s causing the connectivity issues between the VBR server and the appliance, especially since it seems you have a device in your LAN responding on the same IP as the appliance.

Moving the appliance to a dedicated subnet and making it routable via the tunnel would seem to be the best course of action.

I did a bit of searching, and I found a few pages that might be useful to you, I’m not sure how much of this you’ve already set up with your existing deployment:

Configuring Deployment Modes

Configuring Private Network Deployment in Veeam Backup for Azure by ​@wesmrt


CMF
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  • Veeam Legend
  • July 10, 2026

We had an similar issue at a customer, i think the way to go was to install the azure appliance first and then connect VBR to an existing appliance within the internal LAN. When deploying the Appliance from the veeam Console it will always use the external network if I´m not mistaking. 

 

Regards

Chalid


wesmrt
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  • Veeam MVP
  • July 10, 2026

Well, something in your local network may be using the same IP the appliance is using and this is the reason you are not able to connect the VBR to the appliance. 

It's totally ok to use the same range on Azure, you just need to figure out what is responding with the same IP. The Veeam Support is correct, Veeam Backup for Azure dont have anything on port 4343.

You can change the subnet of the appliance and this should also work, but if you are able to find what is using the IP and could change it will be easier.