Understanding Routing Tables

In AWS networking, a routing table is a set of rules that determines how network traffic is directed between different subnets, gateways, and virtual private gateways within a Virtual Private Cloud (VPC). Routing tables play a crucial role in controlling the flow of network traffic in AWS.

To understand routing tables, let's use an analogy from the world of basketball. Imagine a basketball court with multiple players, each representing a different subnet in a VPC. The players need to pass the ball to each other, but they can only pass to players who are in the same team or have a connection with another team through a gateway. The routing table acts as the coach, directing the players on where to pass the ball based on the defined rules.

1class Main {
2  public static void main(String[] args) {
3    // Routing table rules
4    String[][] routingTable = {
5      {"Team 1", "Team 2"},
6      {"Team 1", "Team 3"},
7      {"Team 2", "Team 1"},
8      {"Team 3", "Team 1"},
9      {"Team 4", "Gateway 1"},
10      {"Team 5", "Gateway 1"}
11    };
12
13    // Player passing the ball
14    String player = "Team 1";
15
16    // Check the routing table to find the next player
17    for (String[] rule : routingTable) {
18      if (rule[0].equals(player)) {
19        System.out.println("Pass the ball to " + rule[1]);
20        player = rule[1];
21      }
22    }
23  }
24}

In the code snippet above, we have a routing table represented as a 2D array. The rules define the relationships between different teams (subnets) and gateways. The program simulates a player passing the ball based on the routing table rules. As a player passes the ball, the next player to receive the ball is determined by checking the routing table.

Similarly, in AWS, the routing table maps the rules for network traffic within a VPC. It defines which subnets are connected to each other directly and through virtual private gateways. Each subnet can have a different routing table associated with it, allowing you to control the flow of traffic within the VPC.

Routing tables in AWS can be configured using the AWS Management Console, AWS CLI, or AWS SDKs. You can define routes and associate them with subnets, gateways, or virtual private gateways.

Routing tables provide flexibility and control over network traffic in AWS. By properly configuring the routing tables, you can ensure that network traffic flows efficiently and securely between different subnets and gateways in your VPC.

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class Main {

  public static void main(String[] args) {

    // Routing table rules

    String[][] routingTable = {

      {"Team 1", "Team 2"},

      {"Team 1", "Team 3"},

      {"Team 2", "Team 1"},

      {"Team 3", "Team 1"},

      {"Team 4", "Gateway 1"},

      {"Team 5", "Gateway 1"}

    };

​

    // Player passing the ball

    String player = "Team 1";

​

    // Check the routing table to find the next player

    for (String[] rule : routingTable) {

      if (rule[0].equals(player)) {

        System.out.println("Pass the ball to " + rule[1]);

        player = rule[1];

      }

    }

  }

}