Network load balancer
A network load balancer is used to evenly distribute the load across cloud resources. A load balancer is created in a folder and can serve resources from multiple availability zones. Only one target group can be attached to each load balancer. The health of resources in that group is monitored through a health check.
The Yandex.Cloud Load Balancer uses Layer 3 technologies of the OSI model.
Traffic is distributed using the 5-tuple affinity, using the source IP, source port, destination IP, and destination port of the recipient cloud resource, and the protocol type.
When creating a load balancer, a pre-created target group is attached to it with cloud resources that incoming traffic will be distributed across. Each cloud resource in a target group is defined by a pair of internal IPv4 address and the subnet ID. Targets within one group must be located in the same cloud network. Targets within a single availability zone must be located in the same subnet.
By hosting resources in different availability zones, you ensure their fault tolerance: if all the resources within one zone fail, the load balancer will redirect incoming traffic to resources in other zones. For detailed recommendations on how to use a load balancer, see Best practices.
Network load balancer status
A created load balancer can have one of the following statuses:
CREATING: the load balancer is being created.
STARTING: the load balancer is being started.
ACTIVE: the load balancer is running, performing health checks, and routing traffic to the target group resources.
STOPPING: the load balancer is being stopped.
STOPPED: the load balancer is stopped and is not performing health checks or distributing traffic.
DELETING: the load balancer is being deleted.
INACTIVE: the load balancer has no listeners or the target groups attached to it contain no targets. The load balancer is not performing any checks or distributing any traffic.