Basically Amazon giving you it’s software defined network for your own use
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VPC is an isolated network in a region.
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VPC spans all availability zones in a region
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VPC Components
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VPC
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Subnet
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Route Table
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Security Groups
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Network ACLs
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What is Subnet
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Subnets are basically sub networks inside a VPC. It is like network in the network.
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Each subnet can be one availability zone
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What is Internet Gateway
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All the internet access happens through internet gateway
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This is important for all the traffic leaving VPC
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What is Security Group
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Security groups are applied on per instance level.
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We assign security group to VPCs. And every instance running on the VPC can be attached to the security groups which are assigned to the VPC.
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Security groups are one way of controlling which access is allowed to the instances and which traffic may leave the instances. That basically acts like a firewall.
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What is Network Control List (NACL)
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These apply on subnet level
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We can define which traffic may enter the subnet
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Security group is bit more granular, but NACL allows to really configure the whole subnet.
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Routing table
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Route the traffic differently with Route table
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Specify is traffic allowed to reach other instances in the VPC, is it allowed to leave the VPC
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Can control the assignment of public IPs
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Public and Private Subnets
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Private Subnet
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Block outgoing traffic to deny internet access or doesn’t assign any public IPs
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Can use to holds database service. These shouldn’t need to access from internet. They only need to accessed from your web servers.
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Public Subnet
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Allow outgoing traffic to internet or have Public (Elastic) IPs
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Can use to hold web servers which have to be accessible from the internet and which should send traffic to the internet
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NAT Gateway
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Sometimes we still want our private subnet instances can reach out to the internet because they should be install updates of a software fro example. We do this by redirecting outgoing internet access to a NAT gateway instead of blocking it.
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NAT stands for network address translation
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It translates internal IPs to public ones. NAT Gateway has a public IP. Forwards to the internet gateway. Still access the internet indirectly with private instances.
With the netmask (value after slash) we decide how many binary figures are fixed.
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32 is the highest. It means it’s a one IP. Everything is fixed.
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192.168.0.1/16 - 16 will fix the firest two blocks. This means .0.1 will be variable.
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