Amazon VPC Essentials

Amazon VPC Essentials Amazon Virtual Private Cloud (VPC) is a good way to setup an isolated portion of AWS and control the network topology. It is a good way to extend your computer data center and use AWS for burst requirements. In this post, I'll list down the important thing areas any particular one needs to take into account whenever using VPC. This will help one decide the most effective architecture / solution which could fit the given requirement.

Instances Except Cluster Compute Quadruple Extra Large instances and all other Instance types are available within VPC. Needless to say, make sure you check which Instance types can be purchased in a region.

For instance Second generation Standard On-demand instances are available only in US-East

Public and Private Subnets • •

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The VPC network may be divided further in to smaller network segments called as Subnets. Any VPC will have one or more Subnet You can setup a Public Subnet that will have internet connectivity. Instances which launched in a Public Subnet will have outbound and inbound internet connectivity by the Internet Gateway mounted on the Public Subnet Private Subnets are completely locked down. They do not have internet connectivity automatically Create quantity of Public and Private Subnets based upon your architecture. Place all public facing servers such as for instance web servers, search servers in people subnet.

Security Groups VPC Security Groups are very different from normal Amazon EC Security Groups. With EC2 Security Groups you are able to control the ingress into your EC2 Instance. With VPC Security Groups, you have the option to regulate both inbound and outbound traffic. When something isn't accessible you have to check both inbound and outbound rules emerge the VPC Security Group

ELB Security Group Once you launch an ELB within VPC, you have the option to specify a VPC Security Group to be attached with the ELB. This is not readily available for ELB launched outside VPC in normal EC2. With this additional option, you are able to control usage of specific ELB ports from specific IP sources. On the backend EC2 Instances'Security Group, you are able to allow usage of the VPC Security Group that you associated with the ELB

Internal ELB Once you launch an ELB within VPC, you also have additional option to launch it being an "Internal Load Balancer ".You should use an "Internal Load Balancer" to load balance your application tier on the internet tier above.

NAT Instance Automatically the Private Subnets in a VPC do not have internet connectivity. They can't be accessed over the internet and neither would they make outbound connections to internet resources. But let's say you have setup a database on an EC2 Instance in the Private Subnet and have implemented a backup mechanism. You'd wish to push the backups to Amazon S3. But the Private Subnet's cannot access S3 while there is no internet connectivity. You can get it by placing a NAT Instance.

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Through NAT Instance outbound connectivity for Private Subnet Instances may be achieved. The Instances will still not be reachable from the web (inbound) You need to configure the VPC Routing Table to enable all outbound internet traffic for the Private Subnet to feel the NAT Instance AWS supplies a ready NAT AMI (ami-f619c29f) which you should use to launch the NAT Instance You could have only 1 NAT Instance per VPC Since you can have only 1 NAT Instance per VPC, you will need to be aware that it becomes a Single Point Of Failure in the architecture. If the architecture depends on the NAT Instance for just about any critical connectivity, it's a place to be reviewed And you're limited by the bandwidth accessibility to an individual NAT Instance. So do not build architecture that may have internet bandwidth requirements from the Private Subnet with NAT

Elastic Network Interface This is a powerful feature of VPC which enables you to solve many problems around licensing, hosting multiple SSL websites, etc...

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You can connect many ENI's per Instance essentially creating many private IPs and possibility of attaching multiple EIP's per Instance If you can find products which have licenses associated with the MAC address, you can now set the MAC address to the ENI and have the EC2 Instance derive the them from ENI

Private IP and Elastic IP •

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You can fix the Private IP of the Instance whenever you launch Instances within the VPC. Let's say, you want to launch multiple tiers (web servers and search servers) within a Subnet and have multiple Instances for each tier. when you launch any Web Server Instance should use one of the private IPs from the logical list. This will assist in management of the potentially vast quantity of Instances Private IP of an Instance will not change if you start and stop the Instance In the event that you attach an Elastic IP to the Instance, the EIP doesn't change if you stop and start the Instance

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