Update migrate-from-classic-vnet.md

Author: xuesongyuan

articles/active-directory-domain-services/migrate-from-classic-vnet.md

@@ -39,8 +39,6 @@ As you prepare for migration, there are some considerations around the availabil
 
 The domain controller IP addresses for a managed domain change after migration. This change includes the public IP address for the secure LDAP endpoint. The new IP addresses are inside the address range for the new subnet in the Resource Manager virtual network.
 
-If you need to roll back, the IP addresses may change after rolling back.
-
 Azure AD DS typically uses the first two available IP addresses in the address range, but this isn't guaranteed. You can't currently specify the IP addresses to use after migration.
 
 ### Account lockout
@@ -114,13 +112,6 @@ Before you begin the migration process, complete the following initial checks an
 
     Note that the **CorpNetSaw** service tag isn't available by using Azure portal, and the network security group rule for **CorpNetSaw** has to be added by using [PowerShell](powershell-create-instance.md#create-a-network-security-group).
 
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-1. Check the managed domain health in the Azure portal. If you have any alerts for the managed domain, resolve them before you start the migration process.
-1. Optionally, if you plan to move other resources to the Resource Manager deployment model and virtual network, confirm that those resources can be migrated. For more information, see [Platform-supported migration of IaaS resources from Classic to Resource Manager][migrate-iaas].
-
-    > [!NOTE]
-    > Don't convert the Classic virtual network to a Resource Manager virtual network. If you do, there's no option to roll back or restore the managed domain.
-
 ## Perform offline migration
 
 Azure PowerShell is used to perform offline migration of the managed domain: