Add Limitations for FastPath

Author: derekolo

articles/expressroute/about-fastpath.md

@@ -5,7 +5,7 @@ services: expressroute
 author: duongau
 ms.service: azure-expressroute
 ms.topic: conceptual
-ms.date: 09/02/2024
+ms.date: 11/7/2024
 ms.author: duau
 ms.custom: template-concept, references_regions, engagement-fy23
 ---
@@ -40,6 +40,10 @@ While FastPath supports many configurations, it doesn't support the following fe
 
 * Load Balancers: If you deploy an Azure internal load balancer in your virtual network or the Azure PaaS service you deploy in your virtual network, the network traffic from your on-premises network to the virtual IPs hosted on the load balancer is sent to the virtual network gateway.
 
+* Gateway Transit: If you deploy two peered hub virtual networks connected to one circuit, you need to make sure to set the Allow Gateway Transit on the virtual network peering to false, otherwise you will experience connectivity issues.
+
+* Use Remote Gateway: If you deploy a spoke vnet peered to two hub vnets, you can only use one hub gateway as the remote gateway. If you use both as a remote gateway, you will experience connectivity issues. 
+
 * Private Link: FastPath Connectivity to a private endpoint or Private Link service over an ExpressRoute Direct circuit is supported for limited scenarios. For more information, see [enable FastPath and Private Link for 100-Gbps ExpressRoute Direct](expressroute-howto-linkvnet-arm.md#fastpath-virtual-network-peering-user-defined-routes-udrs-and-private-link-support-for-expressroute-direct-connections). FastPath connectivity to a Private endpoint/Private Link service isn't supported for ExpressRoute partner provider circuits.
 
 * DNS Private Resolver: Azure ExpressRoute FastPath doesn't support connectivity to [DNS Private Resolver](../dns/dns-private-resolver-overview.md).