When an instance is created on AWS, one of the first steps is to create a Route Table. The Route Table defines the route for each Destination. In the following diagram the Instance has two routes, one for 10.20.0.0/16, which is the VPC boundary (local network). Any traffic within 10.20.0.0/16 is considered a local connection. The other route is for 0.0.0.0/0 which will allow IP traffic to route outside the local VPC boundary (to other VPCs or the Internet). To connect to the internet either an Internet Gateway is needed (in the case of a public subnet) or a NAT Gateway should be specified (in the case of a private subnet).

Finding the Active Node within the VPC

When it comes to finding an active node in a clustering environment, we must define a virtual IP address outside of the VPC CIDR so that a route can be defined. In fact, defining a Virtual IP means creating a new Destination in the Route table.

Once a new destination outside of VPC CIDR has been defined, LifeKeeper can change the target of this route to the active node (either 10.20.1.10 or 10.20.2.10 in the example configuration shown above). A client node should simply look for 10.10.10.10 as the destination and the routing table guides the traffic to the active node. The routing table is updated dynamically by SIOS’s Recovery Kit for EC2.

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