Application Gateway

Question

Hi ,

I have already listener port 443 with basic , do i able to create 3 more listener port-443 with multi-site ?

Answer 1

Yes. Multiple listeners can share the same frontend port (443) on an Application Gateway, as long as they differ by listener type/host name.

To host multiple sites on port 443:

1. Keep the existing basic listener on port 443 (or change it if needed).
2. Create three new multi-site HTTPS listeners, all using:
   • The same frontend IP
   • The same frontend port: 443
   • Listener type: Multi-site
   • A unique host name (for example, site1.contoso.com, site2.contoso.com, site3.contoso.com).
3. For each multi-site listener, create a request routing rule that points to the appropriate backend pool.
4. Ensure DNS for each hostname points to the Application Gateway frontend IP.

Listener processing order/priority is important:

• For v1 SKU: multi-site listeners must be listed before the basic listener; otherwise, the basic listener will catch all traffic on 443.
• For v2 SKU: assign higher priority (lower numeric value) to the multi-site listeners than to the basic listener so that host-based rules are evaluated first.

This way, all four listeners can coexist on port 443, and traffic is routed by host header to the correct backend.

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References:

• Application Gateway listener configuration
• Application Gateway multi-site hosting
• Application gateway components
• Azure Application Gateway features
• Tutorial: Create and configure an application gateway to host multiple web sites using the Azure portal
• Integrate an ILB App Service Environment with Azure Application Gateway

Answer 2

Hello @ A, Kowsalya (Cognizant)

Thank you for reaching out to Microsoft Q&A.

Yes, you can definitely create additional listeners on port 443 alongside your existing basic listener. The recommended approach is to use Multi-site listeners, which allow you to host multiple websites on the same IP address and port by differentiating them based on the hostname (host header).

Recommended Solution:

• Keep your current Basic listener as a fallback (catch-all) if needed.
• Create three new Multi-site listeners on the same frontend port 443.
• For each listener, specify the respective hostname (e.g., site1.example.com, site2.example.com, etc.) and attach the appropriate SSL certificate.
• Then create a routing rule for each listener pointing to the correct backend pool.

Place the multi-site rules higher in priority than the basic rule so that hostname-based routing takes precedence.

Official Microsoft Documentation:

• Multiple-site hosting with Application Gateway
• Configure listeners
• Tutorial: Host multiple websites using the Azure portal

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