Merge pull request #282091 from siddomala/ECMPchange

Adding ECMP enablement and NVA limitations

Author: prmerger-automator[bot]

articles/route-server/expressroute-vpn-support.md

@@ -41,8 +41,9 @@ If you enable BGP on the VPN gateway, the gateway learns *On-premises 1* routes
 
 :::image type="content" source="./media/expressroute-vpn-support/expressroute-and-vpn-with-route-server.png" alt-text="Diagram showing ExpressRoute and VPN gateways exchanging routes through Azure Route Server.":::
 
-> [!NOTE] 
-> When the same route is learned over ExpressRoute, Azure VPN or an SDWAN appliance, the ExpressRoute network will be preferred by default. You can configure routing preference to influence Route Server route selection. For more information, see [Routing preference (preview)](hub-routing-preference.md).
+## Considerations
+* When the same route is learned over ExpressRoute, Azure VPN or an SDWAN appliance, the ExpressRoute network will be preferred by default. You can configure routing preference to influence Route Server route selection. For more information, see [Routing preference (preview)](hub-routing-preference.md).
+* If **branch-to-branch** is enabled and your on-premises advertises a route with Azure BGP community 65517:65517, then the ExpressRoute gateway will drop this route. 
 
 ## Related content
 

articles/route-server/peer-route-server-with-virtual-appliance.md

@@ -218,6 +218,9 @@ In this section, you configure BGP settings on the VM so it acts as an NVA and c
 1. Once you add the NVA as a peer, the **Peers** page shows the **myNVA** as a peer:
 
     :::image type="content" source="./media/peer-route-server-with-virtual-appliance/route-server-peers.png" alt-text="Screenshot that shows the peers of a Route Server." lightbox="./media/peer-route-server-with-virtual-appliance/route-server-peers.png":::
+
+ > [!NOTE]
+ > - Azure Route Server supports BGP peering with NVAs that are deployed in the same VNet or a directly peered VNet. Configuring BGP peering between an on-premises NVA and Azure Route Server is not supported. 
     
 ## Check learned routes
 

articles/virtual-wan/scenario-bgp-peering-hub.md

@@ -30,7 +30,9 @@ The virtual hub router now also exposes the ability to peer with it, thereby exc
 
 **Considerations**
 
-* You can't peer a virtual hub router with Azure Route Server provisioned in a virtual network.
+* You can only peer the virtual hub router with NVAs that are deployed in directly connected VNets. 
+  * Configuring BGP peering between an on-premises NVA and the virtual hub router is not supported.  
+  * Configuring BGP peering between an Azure Route Server and the virtual hub router is not supported. 
 * The virtual hub router only supports 16-bit (2 bytes) ASN.
 * The virtual network connection that has the NVA BGP connection endpoint must always be associated and propagating to defaultRouteTable. Custom route tables aren't supported at this time.
 * The virtual hub router supports transit connectivity between virtual networks connected to virtual hubs. This has nothing to do with this feature for BGP peering capability as Virtual WAN already supports transit connectivity. Examples:

articles/virtual-wan/virtual-wan-faq.md

@@ -335,6 +335,10 @@ When an ExpressRoute circuit is connected to a virtual hub, the Microsoft Edge r
 
 For any reason, if the VPN connection becomes the primary medium for the virtual hub to learn routes from (e.g failover scenarios between ExpressRoute and VPN), unless the VPN site has a longer AS Path length, the virtual hub will continue to share VPN learned routes with the ExpressRoute gateway. This causes the Microsoft Edge routers to prefer VPN routes over on-premises routes.
 
+### Does ExpressRoute support Equal-Cost Multi-Path (ECMP) routing in Virtual WAN?
+
+When multiple ExpressRoute circuits are connected to a Virtual WAN hub, ECMP enables traffic from spoke virtual networks to on-premises over ExpressRoute to be distributed across all ExpressRoute circuits advertising the same on-premises routes. To enable ECMP for your Virtual WAN hub, please reach out to [email protected] with your Virtual WAN hub resource ID. 
+
 ### <a name="expressroute-bow-tie"></a>When two hubs (hub 1 and 2) are connected and there's an ExpressRoute circuit connected as a bow-tie to both the hubs, what is the path for a VNet connected to hub 1 to reach a VNet connected in hub 2?
 
 The current behavior is to prefer the ExpressRoute circuit path over hub-to-hub for VNet-to-VNet connectivity. However, this isn't encouraged in a Virtual WAN setup. To resolve this, you can do one of two things: