Merge pull request #87059 from Dekor86/patch-2

Update expressroute-howto-coexist-resource-manager.md

Author: ktoliver

articles/expressroute/expressroute-howto-coexist-resource-manager.md

@@ -131,7 +131,11 @@ This procedure walks you through creating a VNet and Site-to-Site and ExpressRou
    ```azurepowershell-interactive
    $azureVpn = New-AzVirtualNetworkGateway -Name "VPNGateway" -ResourceGroupName $resgrp.ResourceGroupName -Location $location -IpConfigurations $gwConfig -GatewayType "Vpn" -VpnType "RouteBased" -GatewaySku "VpnGw1" -Asn $VNetASN
    ```
-   
+
+   > [!NOTE]
+   > For coexisting gateways, you must use the default ASN of 65515. See [limits and limitations](#limits-and-limitations).
+   > 
+
     You can find the BGP peering IP and the AS number that Azure uses for the VPN gateway in $azureVpn.BgpSettings.BgpPeeringAddress and $azureVpn.BgpSettings.Asn. For more information, see [Configure BGP](../vpn-gateway/vpn-gateway-bgp-resource-manager-ps.md) for Azure VPN gateway.
 5. Create a local site VPN gateway entity. This command doesn’t configure your on-premises VPN gateway. Rather, it allows you to provide the local gateway settings, such as the public IP and the on-premises address space, so that the Azure VPN gateway can connect to it.