Azure VPN through Web Proxy has stopped working

Lab Coat1 6

Simple problem, simple configuration.

Am working on a Windows 10 test system. Trying to run the Azure VPN Client through a web proxy.  
Clients work fine when the test system is connected to the Internet, but we do not want to allow that.
 1. This worked earlier in the week.  But stopped working after switching the client over to a direct internet connection and then back.
 2. Should be simple. Right?
 3. The proxy only registers connect attempts when running Diagnostics from the client.  And not from clicking on Connect.
 4. Additionally, running ipconfig /displaydns does not display the VPN server address, until I run Diagnostics.
 5. Dns resolution is working on the client.
 6. Have multiple connections on two different Azure VPNs.  All exhibit the same behavior.  Two using certificate authentication. One use AAD authentication.
 7. Edge and Firefox have no issues using the proxy, when configured in Internet Settings or within the browser.
 8. Have also downloaded and recreated the connections just to be sure.  No change.
 9. Connections work fine when the client is directly connected to the internet.

Running diagnostics within the Azure VPN Client:
   Internet Access: Available
   Client Credentials : ...Available
   Server Resolvable: DNS resolution failed...no such host known
  (Running nslookup from the command line resolves the server name)
   Server Reachable: ...failed with exception: No such host is known.

Client version 2:1986:50:0
Secondly, what is the deal about needing to install the Azure VPN client in "developer mode"?

ChaitanyaNaykodi-MSFT 23,031 Reputation points Microsoft Employee

2023-04-21T21:51:24.4833333+00:00

@Lab Coat1 Thank you for recahing out on the Microsoft Q&A forum. As Nslookup command resolves the server name successfully. For Azure VPN client can you please check if correrct DNS servers are configure in profile XML? You can follow the steps mentioned here to add any custom DNS servers. Thank you!
Lab Coat1 6 Reputation points

2023-04-24T20:40:47.58+00:00

I have tried that as well with another connection. Same result.
Let me show a different example with the same result.
Same VM, Same Azure VPN Client and connection settings. If i eliminate the web proxy from the setup. As long as I have a single network connection with a public IP address, I can connect to any of the three connections. However, if I have a 2nd interface, connected to an internal network (192...) I cannot connect. (two nics on the client, one connected to the internet, the other to an internal network) The default route (0.0.0.0) does not change, and still points to my internet provider. All that is different in the route table is a /24 addition to the local network. And since the internal network is capable of resolving Internet addresses, I can do an nslookup to either DNS address and resolve the azure.com URL. As mentioned in the original, I have two connection configurations to the same Azure VPN. One with DNS settings and one without. Both work when I am only connected to the Internet. Neither when the 2nd nic is connected to the internal network.
Lab Coat1 6 Reputation points

2023-04-24T21:47:37.39+00:00

After doing much more testing of various configurations. I've decided to leave this to a simple question. Why can I not connect when the client is behind a web proxy server? The rest is noise. Although it is strange that the AnyConnect client has no similar problems connecting through a web proxy. Just a more mature client I suppose. If a proxy is configured, should the Azure client really need to resolve anything via DNS, at least until the initial connection is made and it can resolve via the tunnel?
Lab Coat1 6 Reputation points

2023-04-24T22:14:42.6033333+00:00

For what it is worth. I restored the vm from a snapshot on the 14th. Reloaded the config and created the new connection. Works now through the proxy. Don't know what got hosed. But that's the problem with a test system. Too many changes on a Windows machine can really mess things up. It is working now. Now I can go back to testing forced tunneling. Which does seem to have some holes in it. but now I can recheck them
ChaitanyaNaykodi-MSFT 23,031 Reputation points Microsoft Employee

2023-05-05T02:16:06.5266667+00:00

@Lab Coat1

Glad to know the issue was resolved. If you are still experiencing issues to configure you Windows OS networking. Please make a post here and add the windows-networking tag. Thank you!