What is Route 53 in AWS?

by XDK 4. August 2019 16:32

Amazon Route 53 effectively connects user requests to infrastructure running inAWS – such as Amazon EC2 instances, Elastic Load Balancing load balancers, or Amazon S3 buckets – and can also be used to route users to infrastructure outside of AWS.

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Amazon Web Service

What is AWS NAT Instances & NAT Gateways?

by XDK 4. August 2019 06:35

Explanation:

A NAT (Network Address Translation) instance is, like a bastion host, an EC2 instance that lives in your public subnet. A NAT instance, however, allows your private instances outgoing connectivity to the internet while at the same time blocking inbound traffic from the internet.

A NAT (Network Address Translation) Gateways provide the same functionality as a NAT instance, however, a NAT Gateway is an AWS managed NAT service. As a result, these NAT Gateways offer greater availability and bandwidth and require less configuration and administration.

Comparison of NAT Instances and NAT Gateways

Bastion host : A bastion host is a special-purpose computer on a network specifically designed and configured to withstand attacks. The computer generally hosts a single application, for example a proxy server, and all other services are removed or limited to reduce the threat to the computer.

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Amazon Web Service

CIDR block (Classless Inter-Domain Routing) interpretation

by XDK 4. August 2019 06:09

Explanation:

CIDR (Classless Inter-Domain Routing) notation is a compact representation of an IP address and its associated routing prefix. The notation is constructed from an IP address, a slash ('/') character, and a decimal number. The number is the count of leading 1 bits in the subnet mask. Larger values here indicate smaller networks. CIDR was developed as an alternative to traditional subnetting. The idea is that you can add a specification in the IP address itself as to the number of significant bits that make up the routing or networking portion.

IPv4 CIDR blocks interpretation :

IPv4 : a.b.c.d
Bits : 8.8.8.8 --> 32 bits

CIDR block Notation : a.b.c.d/prefix where prefix is the number of IP address the network can have.

Example : 192.168.100.0/22

IPs calculation for the above CIDR block will be [192(8bits).168(8bits).100(8bits).0(8bits)] = 2^32-22 = 2^10 = 1,024
where 32 -> 8 * 4 bits , 22 -> prefix

Total number of IPs for 192.168.100.0/22 CIDR block will be 1,024

192.168.100.0 -> 255
192.168.101.0 -> 255
192.168.102.0 -> 255
192.168.103.0 -> 255
where 0 -> 255 = 256 IPs

Total IPs = 256 * 4 = 1,024

By default, AWS uses 5 IPs out of these 256 IPs, So the number of IPs released will be 256 - 5 = 251

IPs used by AWS:

0 -> Network Address
1 -> Amazon VPC Routing
2 -> Domain Name System (DNS)
3 -> Future use by AWS
255 -> Broadcasting

In AWS, a subnet can have 1 primary CIDR block and 4 secondary CIDR blocks

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Amazon Web Service

Disclaimer

The information provided here is based on my expreriences, troubleshooting and online/offline findings. It can be used as is on your own risk without any warranties and I impose no rights.

About the author

My name is Xavier Dilip Kumar Jayaraj and I am a Software Configuration Management Engineer with a background in application development, Build & packaging using Install Shield.

Profile in LinkedIn , PCEP-Certified , Azure-DevOps-C1

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