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.
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 trying to serve multiple Azure App Services behind an Application Gateway. These services should only be reachable through the application gateway endpoint. To achieve this, I've done the following:
Added a VNet
Added a subnet, and added all app services to it
Added an application gateway with appropriate rules for pointing to the app service
Added access restrictions to the app service to only allow the subnet of the application gateway, and the public IP of the application gateway
The health probe of the application gateway indicates the service is healthy (and thus reachable), but when I try to make a request to the service trough the gateway using Postman, I get a 403 IP forbidden error. However, when I add my local IP as an allowed IP address to the app service, the request comes through just fine
From what I've read online, adding the public IP of the gateway should be sufficient for allowing access through the gateway, but it seems that requests from my local machine are blocked. Am I getting something fundamentally wrong here?
Edit: I also tried assigning a front-end private IP address to the gateway and adding access for that in the app service, but that also did not work
Edit 2: My configuration
Access restrictions for app service:
access restrictions
Backend pool:
Backend pool
HTTP settings:
HTTP settings
Listener:
Listener
Rule:
Rule
From your description "Added a subnet, and added all app services to it", I assume that you are meaning integrating app with Azure VNet or enable the service endpoint with Microsoft.Web for the subnet. If so, you could remove them. Both are useless in this scenario.
To restrict the access through the gateway, you only need to add the frontend IP address to the Azure App Service access restrictions. For more details, you could refer to this blog https://www.cloudmanav.com/azure/restricting-appservice-accessible-via-appgateway/#
If you have NSG associated with the subnets, you could follow the prerequisites here
https://learn.microsoft.com/en-us/azure/application-gateway/configuration-overview#network-security-groups-on-the-application-gateway-subnet
Edit
You may have redirection configured on your app service or have Azure Active Directory authentication, which causes the redirection. So when redirection happens, the client makes the request directly to app service URL Path contoso.azurewebsites.net/xxx instead of going through the application gateway URL path contoso.com/xxx.
To fix it, you could use a custom domain name to pass the same host name that the application gateway receives to the app service as well, instead of doing a host override. Get more details about this solution here.
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 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.
I have created the External facing ASE with a single Web App. Trying to place a WAF enabled Application Gateway.
I have configure the Application gateway subnet and frontend to Public facing.
To interconnect the WAF with ASE(APP), i have set the target of the App hostname (FQDN) in the Backend pool. After mapping the target, i have verified the backendpool health which states Healthy.
Now i tried to access the Frontend IP and FQDN of Application gateway, i'm getting the below error
"The resource you are looking for has been removed, had its name changed, or is temporarily unavailable."
action taken - Tried without NSG and also allowing NSG in ASE subnet
Need your help, I'm in middle of the Environment setup.
Suspect the hostname resolution is missig and not sure how to overcome this block
"The resource you are looking for has been removed, had its name changed, or is temporarily unavailable."
Every Azure Web App has a collection of host names. A request will be transfer to the dedicated server instance depends on the host name in HTTP request message. If the host name doesn't match one of the host names which configured in Azure portal. The Azure Web App can't be reached.
You could view the default host name in Azure portal.
Since you accessed your Web App by Frontend IP or FQDN of Application gateway, their host names will not match the host name of your Web App.
There are 2 ways to fix it.
To simple test your Application gateway, you could be able to use something like ModHeader Chrome extension to open the public IP address/hostname of the Application Gateway in the browser, and pass in the host name of your Web App you configured on the Web App as a Host Header and the website should come up.
Register a custom domain(For example, abcd.com) in a domain provider(For example, Godaddy). In the DNS setting of your domain, add A record to the IP address of your Application gateway.
After that, you also need to add host name by click add host name button in Azure portal.