An internet gateway is a horizontally scaled, redundant, and highly available VPC component that allows communication between your VPC and the internet. It supports IPv4 and IPv6 traffic. It does not cause availability risks or bandwidth constraints on your network traffic. Show
An internet gateway enables resources in your public subnets (such as EC2 instances) to connect to the internet if the resource has a public IPv4 address or an IPv6 address. Similarly, resources on the internet can initiate a connection to resources in your subnet using the public IPv4 address or IPv6 address. For example, an internet gateway enables you to connect to an EC2 instance in AWS using your local computer. An internet gateway provides a target in your VPC route tables for internet-routable traffic. For communication using IPv4, the internet gateway also performs network address translation (NAT). For communication using IPv6, NAT is not needed because IPv6 addresses are public. For more information, see IP addresses and NAT. There's no additional charge for creating an internet gateway. Enable internet accessTo enable access to or from the internet for instances in a subnet in a VPC using an internet gateway, you must do the following.
Public and private subnets If a subnet is associated with a route table that has a route to an internet gateway, it's known as a public subnet. If a subnet is associated with a route table that does not have a route to an internet gateway, it's known as a private subnet. In your public subnet's route table, you can specify a route for the internet gateway to all destinations not explicitly known to the route table ( IP addresses and NAT To enable communication over the internet for IPv4, your instance must have a public IPv4 address. You can either configure your VPC to automatically assign public IPv4 addresses to your instances, or you can assign Elastic IP addresses to your instances. Your instance is only aware of the private (internal) IP address space defined within the VPC and subnet. The internet gateway logically provides the one-to-one NAT on behalf of your instance, so that when traffic leaves your VPC subnet and goes to the internet, the reply address field is set to the public IPv4 address or Elastic IP address of your instance, and not its private IP address. Conversely, traffic that's destined for the public IPv4 address or Elastic IP address of your instance has its destination address translated into the instance's private IPv4 address before the traffic is delivered to the VPC. To enable communication over the internet for IPv6, your VPC and subnet must have an associated IPv6 CIDR block, and your instance must be assigned an IPv6 address from the range of the subnet. IPv6 addresses are globally unique, and therefore public by default. In the following diagram, the subnet in Availability Zone A is a public subnet. The route table for this subnet has a route that sends all internet-bound IPv4 traffic to the internet gateway. The instances in the public subnet must have public IP addresses or Elastic IP addresses to enable communication with the internet over the internet gateway. For comparison, the subnet in Availability Zone B is a private subnet because its route table does not have a route to the internet gateway. Instances in the private subnet can't communicate with the internet over the internet gateway, even if they have public IP addresses. To provide your instances with internet access without assigning them public IP addresses, you can use a NAT device instead. A NAT device enables instances in a private subnet to connect to the internet, but prevents hosts on the internet from initiating connections with the instances. For more information, see Connect to the internet or other networks using NAT devices. Internet access for default and nondefault VPCs The following table provides an overview of whether your VPC automatically comes with the components required for internet access over IPv4 or IPv6.
For more information about default VPCs, see Default VPCs. For more information about creating a VPC, see Create a VPC. For more information about IP addressing in your VPC, and controlling how instances are assigned public IPv4 or IPv6 addresses, see IP addressing. When you add a new subnet to your VPC, you must set up the routing and security that you want for the subnet. Access the internet from a subnet in your VPCThe following describes how to support internet access from a subnet in your VPC using an internet gateway. To remove internet access, you can detach the internet gateway from your VPC and then delete it. Tasks
Create a subnetTo add a subnet to your VPC
For more information, see Subnets for your VPC. Create and attach an internet gatewayAfter you create an internet gateway, attach it to your VPC. To create an internet gateway and attach it to your VPC
Create a custom route tableWhen you create a subnet, we automatically associate it with the main route table for the VPC. By default, the main route table doesn't contain a route to an internet gateway. The following procedure creates a custom route table with a route that sends traffic destined outside the VPC to the internet gateway, and then associates it with your subnet. To create a custom route table
For more information, see Configure route tables. Create a security group for internet accessBy default, a VPC security group allows all outbound traffic. You can create a new security group and add rules that allow inbound traffic from the internet. You can then associate the security group with instances in the public subnet. To create a security group and associate it with an instance
For more information, see Control traffic to resources using security groups. Assign an Elastic IP address to an instanceAfter you've launched an instance into the subnet, you must assign it an Elastic IP address if you want it to be reachable from the internet over IPv4. If you assigned a public IPv4 address to your instance during launch, then your instance is reachable from the internet, and you do not need to assign it an Elastic IP address. For more information about IP addressing for your instance, see IP addressing. To allocate an Elastic IP address and assign it to an instance using the console
For more information, see Associate Elastic IP addresses with resources in your VPC. Detach an internet gateway from your VPCIf you no longer need internet access for instances that you launch into a nondefault VPC, you can detach an internet gateway from a VPC. You can't detach an internet gateway if the VPC has resources with associated public IP addresses or Elastic IP addresses. To detach an internet gateway
Delete an internet gatewayIf you no longer need an internet gateway, you can delete it. You can't delete an internet gateway if it's still attached to a VPC. To delete an internet gateway
API and command overviewYou can perform the tasks described on this page using the command line or an API. For more information about the command line interfaces and a list of available API actions, see Working with Amazon VPC. What is the default gateway for 192.168 network?The router in the Internet will not forward packet with 192.168. x.x as destination address. The default gateway is 192.168. 0.1.
Which is the process of translating the private IP address to a public IP address so that it can be routed across the Internet?A Network Address Translation (NAT) is the process of mapping an internet protocol (IP) address to another by changing the header of IP packets while in transit via a router.
Which address can be assigned to a host computer?An IP address is a 32-bit number. It uniquely identifies a host (computer or other device, such as a printer or router) on a TCP/IP network. IP addresses are normally expressed in dotted-decimal format, with four numbers separated by periods, such as 192.168. 123.132.
Which protocol can configure a computer's IP address and subnet mask automatically?DHCP. DHCP is the Dynamic Host Configuration Protocol. It is used to automatically provide IP addressing information to clients. A DHCP server can assign IP addresses, subnet masks, a DNS server address, and much more.
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