Tag Variables
You can use a variable to set the value of a defined tag. When you add the tag to a resource, the variable resolves to the data it represents. You can use tag variables in defined tags and default tags.
Supported Tag Variables
The following tag variables are supported.
${iam.principal.name} The name of the principal that tagged the resource
${iam.principal.type} The type of principal that tagged the resource.
${oci.datetime} The date and time that the tag was created.
Consider the following example:
Operations.CostCenter=" ${iam.principal.name} at ${oci.datetime} "
Operations is the namespace, CostCenter is the tag key, and the tag value contains two tag variables ${iam.principal.name} and ${oci.datetime} . When you add this tag to a resource, the variable resolves to your user name (the name of the principal that applied the tag) and a time date stamp for when you added the tag.
user_name at 2019-06-18T18:00:57.604Z
The variable is replaced with data at the time you apply the tag. If you later edit the tag, the variable is gone and only the data remains. You can edit the tag value in all the ways you would edit any other tag value. To create a tag variable, you must use a specific format.
${<variable>} Type a dollar sign followed by open and close curly brackets. The tag variable goes between the curly brackets. You can use tag variables with other tag variables and with string values. Tag defaults let you specify tags to be applied automatically to all resources, at the time of creation, in a specific compartment. This feature allows you to ensure that appropriate tags are applied at resource creation without requiring the user who is creating the resource to have access to the tag namespaces.
https://docs.cloud.oracle.com/en-us/iaas/Content/Tagging/Tasks/managingtagdefaults.htm

An internet gateway is an optional virtual router you can add to your VCN to enable direct connectivity to the internet. Resources that need to use the gateway for internet access must be in a public subnet and have public IP addresses. Each public subnet that needs to use the internet gateway must have a route table rule that specifies the gateway as the target. For traffic to flow between a subnet and an internet gateway, you must create a route rule accordingly in the subnet's route table (for example, destination CIDR = 0.0.0.0/0 and target = internet gateway).
Dynamic Routing Gateway (DRG) is A virtual edge router attached to your VCN. Necessary for private peering. The DRG is a single point of entry for private traffic coming in to your VCN,After creating the DRG, you must attach it to your VCN and add a route for the DRG in the VCN's route table to enable traffic flow.

Managing Traffic Management GEOLOCATION Steering Policies
Geolocation steering policies distribute DNS traffic to different endpoints based on the location of the end user. Customers can define geographic regions composed of originating continent, countries or states/provinces (North America) and define a separate endpoint or set of endpoints for each region.
The Health Checks service allows you to monitor the health of IP addresses and hostnames, as measured from geographic vantage points of your choosing, using HTTP and ping probes. After configuring a health check, you can view the monitor's results. The results include the location from which the host was monitored, the availability of the endpoint, and the date and time the test was performed.
Also you can Combine Managing Traffic Management GEOLOCATION Steering Policies with Oracle Health Checks to fail over from one region to another The Load Balancing service provides health status indicators that use your health check policies to report on the general health of your load balancers and their components.
if you misconfigure the health check Protocol between the Load balancer and backend set that can lead to not get an accurate response as example below If you run a TCP-level health check against an HTTP service, you might not get an accurate response. The TCP handshake can succeed and indicate that the service is up even when the HTTP service is ly configured or having other issues. Although the health check appears good customers might experience transaction failures.