Merge pull request #262284 from vhorne/fw-ki

change title, add link at top

Author: v-regandowner

articles/firewall/firewall-known-issues.md

@@ -1,6 +1,6 @@
 ---
-title: Azure Firewall known issues
-description: Learn about Azure Firewall known issues.
+title: Azure Firewall known issues and limitations
+description: Learn about Azure Firewall known issues and limitations.
 services: firewall
 author: vhorne
 ms.service: firewall
@@ -9,10 +9,12 @@ ms.date: 10/02/2023
 ms.author: victorh
 ---
 
-# Azure Firewall known issues
+# Azure Firewall known issues and limitations
 
 This article list the known issues for [Azure Firewall](overview.md). It is updated as issues are resolved.
 
+For Azure Firewall limitations, see [Azure subscription and service limits, quotas, and constraints](../azure-resource-manager/management/azure-subscription-service-limits.md#azure-firewall-limits).
+
 ## Azure Firewall Standard
 
 Azure Firewall Standard has the following known issues:
@@ -31,7 +33,7 @@ Azure Firewall Standard has the following known issues:
 |With secured virtual hubs, availability zones can only be configured during deployment.| You can't configure Availability Zones after a firewall with secured virtual hubs has been deployed.|This is by design.|
 |SNAT on inbound connections|In addition to DNAT, connections via the firewall public IP address (inbound) are SNATed to one of the firewall private IPs. This requirement today (also for Active/Active NVAs) to ensure symmetric routing.|To preserve the original source for HTTP/S, consider using [XFF](https://en.wikipedia.org/wiki/X-Forwarded-For) headers. For example, use a service such as [Azure Front Door](../frontdoor/front-door-http-headers-protocol.md#from-the-front-door-to-the-backend) or [Azure Application Gateway](../application-gateway/rewrite-http-headers-url.md) in front of the firewall. You can also add WAF as part of Azure Front Door and chain to the firewall.
 |SQL FQDN filtering support only in proxy mode (port 1433)|For Azure SQL Database, Azure Synapse Analytics, and Azure SQL Managed Instance:<br><br>SQL FQDN filtering is supported in proxy-mode only (port 1433).<br><br>For Azure SQL IaaS:<br><br>If you're using nonstandard ports, you can specify those ports in the application rules.|For SQL in redirect mode (the default if connecting from within Azure), you can instead filter access using the SQL service tag as part of Azure Firewall network rules.
-|Outbound SMTP traffic on TCP port 25 is blocked|Outbound email messages that are sent directly to external domains (like `outlook.com` and `gmail.com`) on TCP port 25 can be blocked by the Azure platform. This is the default platform behavior in Azure, Azure Firewall doesn't introduce any more specific restriction. |Use authenticated SMTP relay services, which typically connect through TCP port 587, but also supports other ports.  For more information, see [Troubleshoot outbound SMTP connectivity problems in Azure](../virtual-network/troubleshoot-outbound-smtp-connectivity.md).<br><br>Another option is to deploy Azure Firewall in a standard Enterprise Agreement (EA) subscription. Azure Firewall in an EA subscription can communicate with public IP addressess using outbound TCP port 25. Currently, it may also work in other subscription types, but it's not guaranteed to work. For private IP addressess like virtual networks, VPNs, and Azure ExpressRoute, Azure Firewall supports an outbound connection on TCP port 25.
+|Outbound SMTP traffic on TCP port 25 is blocked|Outbound email messages that are sent directly to external domains (like `outlook.com` and `gmail.com`) on TCP port 25 can be blocked by the Azure platform. This is the default platform behavior in Azure, Azure Firewall doesn't introduce any more specific restriction. |Use authenticated SMTP relay services, which typically connect through TCP port 587, but also supports other ports.  For more information, see [Troubleshoot outbound SMTP connectivity problems in Azure](../virtual-network/troubleshoot-outbound-smtp-connectivity.md).<br><br>Another option is to deploy Azure Firewall in a standard Enterprise Agreement (EA) subscription. Azure Firewall in an EA subscription can communicate with public IP addresses using outbound TCP port 25. Currently, it may also work in other subscription types, but it's not guaranteed to work. For private IP addresses like virtual networks, VPNs, and Azure ExpressRoute, Azure Firewall supports an outbound connection on TCP port 25.
 |SNAT port exhaustion|Azure Firewall currently supports 2496 ports per Public IP address per backend Virtual Machine Scale Set instance. By default, there are two Virtual Machine Scale Set instances. So, there are 4992 ports per flow (destination IP, destination port and protocol (TCP or UDP).  The firewall scales up to a maximum of 20 instances. |This is a platform limitation. You can work around the limits by configuring Azure Firewall deployments with a minimum of five public IP addresses for deployments susceptible to SNAT exhaustion. This increases the SNAT ports available by five times. Allocate from an IP address prefix to simplify downstream permissions. For a more permanent solution, you can deploy a NAT gateway to overcome the SNAT port limits. This approach is supported for virtual network deployments. <br /><br /> For more information, see [Scale SNAT ports with Azure Virtual Network NAT](integrate-with-nat-gateway.md).|
 |DNAT isn't supported with Forced Tunneling enabled|Firewalls deployed with Forced Tunneling enabled can't support inbound access from the Internet because of asymmetric routing.|This is by design because of asymmetric routing. The return path for inbound connections goes via the on-premises firewall, which hasn't seen the connection established.
 |Outbound Passive FTP may not work for Firewalls with multiple public IP addresses, depending on your FTP server configuration.|Passive FTP establishes different connections for control and data channels. When a Firewall with multiple public IP addresses sends data outbound, it randomly selects one of its public IP addresses for the source IP address. FTP may fail when data and control channels use different source IP addresses, depending on your FTP server configuration.|An explicit SNAT configuration is planned. In the meantime, you can configure your FTP server to accept data and control channels from different source IP addresses (see [an example for  IIS](/iis/configuration/system.applicationhost/sites/sitedefaults/ftpserver/security/datachannelsecurity)). Alternatively, consider using a single IP address in this situation.|

articles/firewall/toc.yml

@@ -228,7 +228,7 @@ items:
   items:
   - name: FAQ
     href: firewall-faq.yml
-  - name: Known issues
+  - name: Known issues and limitations
     href: firewall-known-issues.md
   - name: Author templates
     href: ../azure-resource-manager/templates/syntax.md