I have WAF, Application Gateway and a VM in place in Azure cloud. I have deployed an application in VM, which is running on tomcate and on port 8280.
I have domain name www.abc.com. In DNS entry, www.abc.com is pointing to my Azure App Gateway on port 80.
I am able to access the my application using IP and port. for example:-
http://X.X.X.X:8280/MyApps/page1 and http://X.X.X.X:8280/MyApps/page2.
I am trying to configure App Gateway, so that when I try to open using domain name. My requirement is when I hit www.abc.com, it should redirect to URL www.abc.com/page1. I tried to setup the listener with basic type and also path based. But no success. When I try to hit www.abc.com, it throws error:
502 - Web server received an invalid response while acting as a gateway or proxy server.
The 502 error always shows that there is a firewall restiction from your application gateway instance to your backend VM. You can verify if there are blocking the traffics in the NSG associated with your application gateway subnet or VM subnet. Also, this might be caused by inproperly configuring the custom health probe. You also can get more reasons from this doc.
Moreover, you can confirm you have set the url-based path correctly. Pay attention to the path and port.
Related
We have configured Listeners and add the rules and upload the SSL certificate on Azure portal
But the server is not hitting the URL. Suggest me if there any settings i missed to configure to enable the listeners based routing settings
When you access a host name via the App gateway, the DNS resolves that host name to the public IP address of the App gateway (which should be configured as a CNAME in your DNS or local host files) and then the app gateway uses that host header to find the associated listener. Once it finds the correct listener, it checks the associated rule and use the configured http settings to direct the traffic to the configured backend service.
Without the CNAME mapping in your DNS, the application gateway will not be aware of the host name/domain name that you are using to access the site.
If you have not created a CNAME mapping to your Application gateway's IP in your DNS, you can also make use of host files in your local machine for the name resolution as part of testing.
Reference : https://learn.microsoft.com/en-us/azure/application-gateway/create-multiple-sites-portal#edit-your-hosts-file-for-name-resolution
I'm having an issue with hosting multiple .NET websites on Windows Server/IIS and Azure Application Gateway.
We host multiple sites on a single Azure Windows VM running IIS, sitting behind Azure Application Gateway WAFv2. The VM is connected to App Gateway using a backend pool configured to point to the private IP of the VM, with the VNets peering configured between the App Gateway and VM VNets.
When I stop the default website in IIS, ALL websites then return a '502 Bad Gateway' error from Azure Application Gateway, and the backend health status changes to 'Unhealthy' for the backend pool where the VM resides.
Can anyone tell me why stopping the Default site would cause Application Gateway to error for all sites?
EDIT:
Screenshot of IIS bindings as requested
EDIT 2: Apparently I can't answer my own question, however after working through this with our CSP I have the answer. By default the App Gateway Backend Health check looks at the default IIS site. If you stop that then the Backend Health Check fails and goes Unhealthy. At this point APP Gateway will no longer even ATTEMPT to route any requests, regardless of URL to that backend pool.
If the application gateway has no VMs or virtual machine scale set configured in the back-end address pool, it can’t route any customer request and sends a bad gateway error.
Following the below command to show back-end address pool JSON result.
Get-AzApplicationGateway -Name "SampleGateway" -ResourceGroupName "ExampleResourceGroup"
Here is an official guideline for troubleshooting the 502 error.
https://learn.microsoft.com/en-us/azure/application-gateway/application-gateway-troubleshooting-502#overview
Also, here is a simple troubleshooter.
https://support.microsoft.com/en-us/help/4504111/azure-application-gateway-with-bad-gateway-502-errors
If I were to try and troubleshoot this, I would likely start with a brand new "test" instance of IIS and set up a reverse proxy on port 80 whose only job is to listen to incoming requests to port 80. Those requests would then be forwarded by your reverse proxy to your actual websites bound to different ports (e.g. 81, 82, 83, etc).
The idea here is to have all of your websites running on different ports such that when you stop one of your sites, the others continue to run without a problem.
Given your setup with up to 40 sites hosted in a single instance of IIS, I would only attempt this type of troubleshooting with a brand new "test" instance of IIS.
Create a brand new "test" instance of IIS.
Create a reverse proxy. To do this, create a new site and name it (e.g. rev-proxy) and give it a binding of port 80.
Deploy one actual site (e.g. myfirstsite). Give it a port binding of something other than 80 (e.g. 81).
Double click your rev-proxy site and add a URL Rewrite -> Inbound Rules -> Blank rule. See attached picture. Add a rule such that when a user requests "myfirstsite" that request is forwarded onto port 81. Use the "Test Pattern" button to test your pattern. The image is only a suggestion and your pattern should correspond to the URL your users are using to request your site and not necessarily to the name you give your site in IIS.
An example of a reverse proxy with a URL Rewrite
Found the answer to this after many months of messing about!
With Azure Application Gateway, the default health probes for each backend pool ping and look for a response on the configured IP address or FQDN in the backend pool itself.
In my case this is set to the local IP address of the Virtual machine (when I configured this 18-24 months ago I recall our Azure CSP telling me there was a bug with using the FQDN in the backend pool configuration).
This means, that when the Health Probe is attempting to communicate with the VM, the Default Website in IIS is the only thing configured to respond to any requests on this IP address.
If you stop the Default Site, the Health Probe gets no response to it's requests a the Backend Pool status goes to Unhealthy as you would expect.
The really interesting thing here is that as soon as the Backend Pool Health Probe status goes Unhealthy, Azure Application Gateway ceases to even attempt to route any traffic to the affected backend pool. Instead it immediately reports the 502 Bad gateway error, and will continue to do so until the Health Probe status is corrected and goes back to healthy!
Scenario:
Configured Azure Application Gateway to route traffic to different Azure Web Apps to leverage the Web Application Firewall (WAF).
Initial configuration worked fine except that the final URL in the browser is the {mysite}.azurewebsites.net. I want this to be the custom domain name {subdomain}.{mysite}.com. This was configured by having the backend pool bound to an app service. Changing it to FQDN is not working. Screen shots below.
CNAME is already pointing to the gateway.
Desired result
When someone hits {subdomain}.{mysite}.com (which is already configured to point to the gateway) I should get {subdomain}.{mysite}.com not {mysite}.azurewebsites.net
Current setup:
The gateway is configured with a multi-site listener with its rule pointing to a backend pool and also bound to the http setting.
Listener is listening on {subdomain}.{mysite}.com
Backend pool config
Probe config
Http setting config
The following links provide some partial answers/configurations but none of them worked for me.
Application Gateway - 502 error
https://learn.microsoft.com/en-us/azure/application-gateway/troubleshoot-app-service-redirection-app-service-url
https://learn.microsoft.com/en-us/azure/application-gateway/create-web-app
UPDATE
Here are a list of steps used to configure an azure app service with a custom domain behind the Azure Application Gateway and WAF (Web Application Firewall) using the azure portal UI.
Configure a Backend pool with target pointing to your App Service.
Configure Health Probe with the following settings
Protocol: HTTP or HTTPS
Host: {appservice}.azurewebsites.net
Path: /
Configure Http setting
Use App Service unchecked.
Use custom probe checked.
Pick host name from backend address unchecked (you might have to check this to configure the rule and then uncheck it).
Configure listener
HostName: {subdomain}.{domain}.com (your domain)
Configure basic rule
Bind it to the appropriate http setting, backend pool and listener
Caveat: If there are no http settings with Pick host name from backend checked, you might need to change it, attach it, and then remove that flag again.
Probably, you get a 502 error because you change to FQDN subdomain.mysite.com in the targets of backend pool. However, In this scenario, you have not changed the custom domains in your web app service, you only could access the web site via the default domain mysite.azurewebsites.net. I suggest changing back to the App service in the targets.
Initial configuration worked fine except that the final URL in the
browser is the {mysite}.azurewebsites.net.
Please check if you have an HTTPS Only setting ON in the Custom domains of web app service. This will redirect all Http to Https. For me, usually, it will cause the final URL in the browser is the mysite.azurewebsites.net.
Update
If you have no HTTPS Only on, this issue may happen due to the following main reasons:
You have redirection configured on your App Service. Redirection can be as simple as adding a trailing slash to the request.
You have Azure AD authentication which causes the redirection.
You have enabled “Pick Host Name from Backend Address” switch in the HTTP settings of Application Gateway.
You don’t have your custom domain registered with your App Service.
This issue can be resolved by not having a redirection on the Application side, however, if that’s not possible, you can follow this solution to resolve it.
Register the domain subdomain.mysite.com to the custom domain list of the App Service. For more information, see Map an existing custom DNS name to Azure App Service.
Once that is done, your App Service is ready to accept the hostname subdomain.mysite.com. Now change your CNAME entry in DNS to point it back to Application Gateway’s FQDN. For example, appgw.eastus.cloudapp.azure.com.
Uncheck the checkbox Pick Hostname from Backend HTTP Settings in probe settings. In the hostname field of the probe, enter your App Service's FQDN mysite.azurewebsites.net as the probe requests sent from Application Gateway will carry this in the host header.
Uncheck the checkbox Pick Hostname from Backend Address in your Application Gateway’s HTTP settings.
Associate the custom probe back to the backend HTTP settings and verify the backend health if it is healthy.
Once this is done, Application Gateway should now forward the same hostname subdomain.mysite.com to the App Service and the redirection will happen on the same hostname.
I am trying to protect a web app using a virtual network. So I created network resources as this link describes. Then I created an application gateway as per the instruction of this link.
Finally I did what this link says to configure the web app.
However, when I went to my web app, under the networking I didn't see it being connected to any VNet. It was saying the VNet doesn't have any Virtual Network Gateway. So I created a VNG and then I went back to the web app, networking and connected it to the VNet.
Now under the Application Gateway health prob I expect the health probs to be successful. But I keep getting a 404. I checked my web app log and no request seems to be coming in.
In a nutshell I have the following:
Virtual Network (VNet): 10.0.0.0/16
Virtual Network Gateway (VNG): 10.1.0.0/24
Application Gateway (AG): this has a public IP. I created a CName on mydomain.com to point to this AG
VNet has 3 subnets: Backend SN(10.0.1.0/24), App Gateway SN(10.0.2.0/24) and another called Gateway SN(10.0.0.0/24)
The AG, has a backend pool, HTTP Settings and a Frontend IP
The AG backend pool points to the web app service
The AG HTTP Settings points to port 80, and the Pick hostname from backend address is checked
The AG also has Listener where the hostname is set to mydomain.com
I believe at this stage if I go to mydomain.com then I should see my web app. But I get the error:
502 - Web server received an invalid response while acting as a gateway or proxy server.
There is a problem with the page you are looking for, and it cannot be displayed. When the Web server (while acting as a gateway or proxy) contacted the upstream content server, it received an invalid response from the content server
And the probs still get 404.
Can someone help please?
What fixed it for me was that I need to make sure -PickHostNameFromBackendAddress is set when doing New-AzureRmApplicationGatewayBackendHttpSettings.
I have setup Application Service environment and trying to access WebApps inside App service environment through Application gateway. Below are the steps I followed to create required setup however I am getting "502 - Web server received an invalid response while acting as a gateway or proxy server" error when I hit the URL that is mapped with application gateway public URL
Created Vnet and created App Service environment inside separate subnet, used subdomain name as dev.xyz.com. I used ILB wild card certificate here issued to *.xyz.com
Created app inside App service environment and named it as "dev-web.dev.xyz.com" and added externally accessible DNS name in the custom domain as "dev-web.xyz.com"
Created Application gateway, added Internal IP address of ILB ( App Service Environment) as back end pool
Created App Gateway-HTTP Settings using port 80 and mapped it with custom probe
Created App Gateway-CustomProbe, host name used here is extenally accessible DNS name which is "dev-web.xyz.com"
Created App Gateway-Listner using host name as extenally accessible DNS name which is "dev-web.xyz.com"
Added a basic rule and mapped above resources with each other
I am still not able to access my Web App after acessing dev-web.xyz.com
I am not sure about how port number used to create listner affect the setup or if I am missing anything.
I also want to implement SSL once I am done with above testing, I would appretiate inputs on how to implement that for above setup.
Created App Gateway-Listner using host name as extenally accessible DNS name which is "dev-web.xyz.com"
After created your App Gateway, a default listener is created to bind the front end IP and port 80 for you. The listener means the App Gateway will monitor the requests which were send to the IP address and port and forwarding the requests to the backend resources. Since you add a host name 'dev-web.xyz.com' as its listener. The App Gateway will also monitor the requests which were send to the host. It will cause a infinite loop forwarding due to the listener host is also marked as the backend host.
To fix the error, you need to remove the App Gateway-Listener record which you added.
I was able to resolve the issue by mapping correct port for the listener. Listener won't harm if you have correct rule setup in the configuration.