The role of subnetwork. Currently, this field is only used when
purpose is set to GLOBAL_MANAGED_PROXY or REGIONAL_MANAGED_PROXY.
The value can be set to ACTIVE or BACKUP. An ACTIVE subnetwork is
one that is currently being used for Envoy-based load balancers in a
region. A BACKUP subnetwork is one that is ready to be promoted to
ACTIVE or is currently draining. This field can be updated with a
patch request.
Values:
UNDEFINED_ROLE (0):
A value indicating that the enum field is not
set.
ACTIVE (314733318):
The ACTIVE subnet that is currently used.
BACKUP (341010882):
The BACKUP subnet that could be promoted to
ACTIVE.