In both GCP and Azure, system-generated routes are automatically created by the cloud provider and cannot be directly created or removed by users. However, users can override or supplement system-generated routes with custom routes in both platforms. 

GCP:
  • System-generated routes:
    GCP automatically creates subnet routes and default routes within a VPC. 

  • Custom routes:
    Users can create custom routes to override or supplement system-generated routes, but custom routes cannot override subnet routes, which have higher priority. 

  • Cloud Router:
    GCP provides a service called Cloud Router that facilitates BGP routing and allows for dynamic route sharing between VPCs and other networks, says a LinkedIn post. 

  • Instance Tags:
    GCP allows users to define instance tags to which a specific route should apply, meaning only traffic originating from certain instances will use that route, as explained in a LinkedIn post. 

Azure:
  • System-generated routes:

    .Opens in new tab

    Azure creates default system routes for each subnet within a Virtual Network (VNet). 

  • User-defined routes (UDRs):

    .Opens in new tab

    Azure allows users to create UDRs, which can be used to override or supplement system-generated routes. 

  • Route Tables:

    .Opens in new tab

    UDRs must be associated with a route table and assigned to a specific subnet in Azure. 

  • Next-Hop:

    .Opens in new tab

    Azure and GCP both provide options for the next-hop of a route, which can indicate a cloud service like a VPN gateway or virtual appliance. 

Key Differences:
  • Instance Tags:
    GCP provides the ability to apply routes based on instance tags, which is not available in Azure. 

  • Route Table Association:
    In Azure, UDRs must be associated with a route table and assigned to a subnet, while GCP's routes can be configured centrally for any existing VPC.

  • Cloud Router:
    GCP's Cloud Router provides dynamic routing capabilities and route sharing, which is a key feature for multicloud and hybrid cloud environments.