Building out a VPC Part 2

Following on from my previous post, we’ll now continue building out our VPC and perform some tests to prove all is as it should be (and as secure as it should be).

Security Groups

Security Groups are our firewalls in the AWS cloud, they allow us to permit/deny protocol and port access level.

We’re going to create two new Security Groups, one to permit the outside world across the www into our public facing instance – a web server as an example.

Our second SG will be permitting our EC2/public facing resources to talk to our backend – perhaps we have our database tier in the private addressing space.

Navigate to your VPC Dashboard and select “Security Groups” from the left hand pane.

Create a new Security Group. Give it a useful name, description and associate it with your VPC. Hit “Create”.

Select your newly created SG and add your required rules. This is our web facing instance in our public subnet, therefore for this web server we’re going to allow SSH and HTTP access from the internet.

Here you can see I have added two rules into the “Inbound Rules” tab within the SG. The top rule allows me to SSH into my instances sharing the same Security Group, and the second allows clients to come in over TCP/80 – HTTP.

To prove this SG we’ll spin up an EC2 instance and check two things:

  • If we can SSH into the instance
  • If the instance can get out to the internet.

There are a few details we need to make sure are correct on the “Configure Instance Details” screen, these are:

  • Network – You want the instance provisioned into your VPC
  • Subnet – You want the instance in the correct public subnet we created earlier
  • Auto-assign Public IP – As this is going to be a public facing instance/server, we want a public IP address to be automatically configured for us.

Before we try to SSH to our newly created instance we need to assign it to the Security Group we created earlier for our public facing instances.

Navigate to “Actions > Networking > Change Security Groups”.

Deselect the wizard SG, as that was created when we spun up the instance and select the appropriate SG that was created earlier to permit SSH and HTTP. This step could have been set during instance creation, but I find it easier to do it post as I get a better feel for what the new instance can and can’t do.


Attempt to SSH into the instance via PuTTy. If you’ve not done this before I suggest reading this article as the process if different for MAC and Windows.

Grab your instances public IP address – right hand side of the “Description” tab and head over to PuTTy.

Populate your hostname and save the session for future use if required. Then navigate down the left pane to SSH > Auth and browse for your PPK file which will authenticate you and permit you into the instance.

Head back to the Session window and hit Open, if successful you’ll receive the below screen. If this fails it’s likely to be a PuTTy issue with the ppk file, an Security Group issue or a issue with your instance being in the wrong subnet.

Hit Yes here.

We’ve now successfully SSH’d into our AWS EC2 instance, which resides in our configured subnet, inside our VPC.

Increase your privileges using the command “Sudo Su” – this is a Linux VM we’ve created.

Let’s see if our instance in the public subnet can get out to the internet to Yum repositories for example, to update. We know we can get in, but can it get out?

Looks good.

Web Server

We know we can SSH into our instance, as we’ve just done that, but how can we tell if port 80 (HTTP) is open. To test that we’re going to install Apache onto the instance and create a little web page for us to target.

This command will install Apache onto our instance and turn it into a web server.

Now change directory to /var/www/html and create an index.html file, which will be the file our web server will present when we try and access it over the web!

Type a message, or add some ascii art 😉 and exit and save via a CTRL+x and Return.

As you can see, our newly created index.html file now sits in the /var/www/html directory for us to hit when we browse to our server – all going well.

The final thing to do before testing is to start the httpd service, which will make our web server listen for incoming request on port 80.

We can confirm the server is now listening by looking at it’s open ports

The acid test is bringing up the webpage (index.html) in a browser so let’s try that.

And there we are, we’re now serving web pages to anyone on the internet from our EC2 web server. This sits in our defined subnet, inside our VPC, and is restricted by our Security Groups.

That was another long one, so in part 3 we’ll:

  • Spin up a backend server and drop it into our Private Subnet
  • Secure the backend, so only the instances in our public subnet can talk to it – not anyone on the internet!
  • Create a NAT Gateway, so our instances in the private subnet can get secure internet access.


Building out a VPC Part 1

In AWS a VPC (Virtual Private Cloud) allows you to build out your own piece of the AWS cloud, the way you want it, i.e such as your Data Center schema for example if you’re migrating over.

I’ve been going through the material to recertify my Solutions Architect cert, therefore thought I’d put it down in writing for reference.

Create your CIDR block

Within the console, navigate to “VPC” . Once you’re in the VPC dashboard you can launch the VPC Wizard, but you don’t really learn much going that route. Navigate down the left pane and select “Your VPCs”.

Hit Create VPC and you will be presented with the following screen, which will ask you for certain information.

Give your VPC a useful name and specify your Classless InterDomain Routing block. You can select the radio button to assign an IPv6 block, but I didn’t, and I left Tenancy at Default instead of “Dedicated” as I don’t need my VPC running on dedicated AWS hardware/resource.

If successful you’ll receive:

By creating a new VPC, you’ll automatically receive the following:

  • A new Routing table
  • A new default Network ACL (Access Control List)
  • A new default Security Group.


Next step is to create your individual subnets that will be carved out from your VPC’s CIDR block. On the left hand pane select “Subnets”.

You will find a handful of subnets already listed, but these are the default subnets for the default VPC. The new subnets we create will be in addition to these.

Give the first subnet a useful name, assign it into the new VPC you’ve just created and drop it into an “Availability Zone” of your choosing. I shall be making two subnets – a Public and a Private, therefore each will go into a different AZ for additional resilience.

Follow the same steps for the second, private subnet and hit “Create”. We now have two subnets, one for our Public facing services and a second, Private subnet for our backend.

At the moment we have no means of internet access out of our newly provisioned VPC and Subnets, therefore we need to remedy that so our resources can update/talk out etc.

Routing Table

We don’t want newly provisioned resources in our VPC to use the default routing table, therefore we need to create a new one, associate it with our Public facing subnet and give it a Gateway out.

On the left pane in the VPC Dashboard navigate to:

Give your Routing table a useful name, associate it with your VPC and hit “Create”. Highlighting your newly created Routing table will display a number of tabs:

Select the “Subnet Associations” tab and hit “Edit subnet associations” to link your new, public subnet to this new routing table.

Make sure to select the Public subnet and hit Save, as we are now going to create a Internet Gateway and specify a default route in our Routing table to forward non-local traffic out to the internet via our IGW.

Internet Gateway

Navigate down the left pane of the VPC Dashboard to “Internet Gateways” and create a new IGW.

Highlight your new Internet Gateway and select “Actions -> Attach to VPC”

Select your new VPC and hit “Attach”. Now go back to your Route Tables and highlight your newly created Routing Table for your public subnet.

Go to the Routes tab and then “Edit routes”. Add a new default route with a destination of (anywhere other than the routes you know about), as a Target select your newly created Internet Gateway and hit “Save routes”.

You will now have a default route below your local route, which will forward all non-local traffic to the Internet Gateway.

In Part 2 we’ll finish off by:

  • Creating suitably secure Security Groups for our Public and Private instances.
  • Creating an EC2 instance as a web server and confirming all the routing and necessary security is in place.
  • Creating a NAT Gateway to provide the private subnet with means to get to the internet.

To be continued…


Favourite AWS Services

I’m a fan of Amazon Web Services. Mainly from a technical perspective, as it’s not necessarily cheaper to move from on-prem to on-cloud – so always read the small-print before uplifting your whole datacentre ;). Infact, it interested me so much I sat the Certified Solutions Architect exam last year and thoroughly enjoyed going through the material and labbing along the way.

I like to keep a track of updates to current AWS services, but also new ones that are released and thought I’d highlight 5 of my current favourite offerings.

5. Elastic Compute Cloud (Amazon EC2)


EC2 is the bread and butter of AWS. It provides you with all the compute grunt you could ever wish for or need. Need 5 Linux VMs for a web server cluster? Or how about the ability to auto-scale when demand requires it, then spin those same servers down automatically when demand tails off? Don’t worry, EC2 can do just that, as well as a vast amount more.

To spin up an EC2 instance (VM) you have a few options. You can:

  • Use their quick start utility, which provides you with ~30 of the most popular AMI’s (Amazon Machine Images) to choose from. Think your standard, hardened versions of Amazon Linux, RedHat, SUSE, Fedora and then your Windows and Ubuntu variants too
  • Choose an AMI that you have created yourself, perhaps a specific build of server with pre-install software
  • Head over to the AWS Marketplace and utilise for free, or buy specific software that runs in the cloud. Think F5 from Big-IP, Splunk or Juniper etc
  • Launch a community AMI that has been created by a member of the community

It’s frighteningly easy to get up and running, just make sure to terminate the instance/s when you’re finished playing otherwise the costs can soon start to build without you even knowing.

Intro to EC2 Video

4. Kinesis


If you’re interested in processing or analyzing streams of data – think Twitter for example, then Kinesis and  is a really useful service.

You can use it to build custom applications to collect and analyze streaming data for a bespoke set of needs or requirements. One example could be monitoring Twitter for every time the tag #JustinBieber (whoever he is….) is seen, then pushing that data through Firehose to the analytics engine to present users with personalised content – graphs, diagrams, feeds etc. Powerful stuff.

As per AWS Kinesis FAQs , a Kinesis stream flow:


Amazon Kinesis Streams enables you to build custom applications that process or analyze streaming data for specialized needs. You can continuously add various types of data such as clickstreams, application logs, and social media to an Amazon Kinesis stream from hundreds of thousands of sources. Within seconds, the data will be available for your Amazon Kinesis Applications to read and process from the stream.

3. Trusted Advisor


Trusted Advisor is like having your own AWS architect on-hand, 24 hours a day, to audit your AWS account and tell you where it’s vulnerable, where you could save money and how you could increase performance. Whenever you want.


It’s pretty simple – if you use AWS, you should be using TA.

2. Identity & Access Management


IAM is certainly in the top 3 of the most important AWS services. With it you can pretty much control all access to all of your accounts resources, whether they be groups or individuals.

Straight out of the box you will want to create users (then swallow your root credentials to keep them safe…) and manage their identities by granting generic or bespoke permissions. This way they’ll only have access to the resources they need.

1. Virtual Private Cloud (VPC)


As a Network bod myself, VPC is of real interest to me. It allows you to provision you own isolated CIDR block, allocate subnets and configure routing tables, all within AWS. You can then architect your solutions in a virtual network that you have defined and could, in theory replicate your on-prem, private IP schema’s in the cloud!

You can also create a hardware Virtual Private Network (VPN) connection between your corporate datacenter and your VPC and leverage the AWS cloud as an extension of your corporate datacenter.


I feel that the VPC gives a little bit back to the Network Engineer, as in they’ve just seen half their DC shifted to VM’s in the cloud so still get to play with IP subnetting and IP allocation in the Cloud.

A Quick AWS explanation of VPC can be found here.

If you want more AWS content than any normal person could ever be able to digest, then head over to the AWS YouTube channel.



Website Powered by

Up ↑