added mitigation

Author: siddomala

articles/virtual-wan/about-virtual-hub-routing-preference.md

@@ -49,7 +49,7 @@ This section explains the route selection algorithm in a virtual hub along with
 **Things to note:**
 
 * When there are multiple virtual hubs in a Virtual WAN scenario, a virtual hub selects the best routes using the route selection algorithm described above, and then advertises them to the other virtual hubs in the virtual WAN.
-* For a given set of destination route-prefixes, if the ExpressRoute routes are preferred and the ExpressRoute connection subsequently goes down, then routes from S2S VPN or SD-WAN NVA connections will be preferred for traffic destined to the same route-prefixes. When the ExpressRoute connection is restored, traffic destined for these route-prefixes will continue to prefer the S2S VPN or SD-WAN NVA connections. 
+* For a given set of destination route-prefixes, if the ExpressRoute routes are preferred and the ExpressRoute connection subsequently goes down, then routes from S2S VPN or SD-WAN NVA connections will be preferred for traffic destined to the same route-prefixes. When the ExpressRoute connection is restored, traffic destined for these route-prefixes may continue to prefer the S2S VPN or SD-WAN NVA connections. To prevent this from happening, you need to configure your on-premises device to utilize AS-Path prepending for the routes being advertised to your S2S VPN Gateway and SD-WAN NVA, as you need to ensure the AS-Path length is longer for VPN/NVA routes than ExpressRoute routes. 
 
 ## Routing scenarios