Hi Friends,
I am happy to share that have passed another AWS cloud certification exam. The training and sponsorship was provided by Rackspace Cloud (AWS partner). This exam “AWS Cloud Practitioner” is relatively very simple in comparison to “AWS Solutions Architect“. I finished it in almost half the time 
given in exam.
The certificate is issued by AWS Training and Certification.
Feel free to reach out to me if for any help, assistance, guidance or motivation related to AWS certification.
I am happy to share that I took another step in my cloud journey and finished a 35 hours cloud Architect training by linux academy.
I have explained Auto Scaling with live demo using AWS ASG, SQS and Cloud Watch. Watch this short video to understand the elasticity and power of the cloud.
Completed AWS Cloud Economics course for AWS partners.
https://www.aws.training/Transcript/CompletionCertificateHtml?transcriptid=UwjzmozkW0isbhIswNmhlg2
Thanks to #rackspace and #aws for sponsoring the program.
If you have many instances, managing the firewalls using Network ACL can be very useful. Otherwise, with Security group, you have to manually assign a security group to the instances.
State: Stateful or Stateless
Security groups are stateful: This means any changes applied to an incoming rule will be automatically applied to the outgoing rule. e.g. If you allow an incoming port 80, the outgoing port 80 will be automatically opened.
Network ACLs are stateless: This means any changes applied to an incoming rule will not be applied to the outgoing rule. e.g. If you allow an incoming port 80, you would also need to apply the rule for outgoing traffic.
Rules: Allow or Deny
Security group support allow rules only (by default all rules are denied). e.g. You cannot deny a certain IP address from establishing a connection.
Network ACL support allow and deny rules. By deny rules, you could explicitly deny a certain IP address to establish a connection example: Block IP address 123.201.57.39 from establishing a connection to an EC2 Instance.
Rule process order
All rules in a security group are applied whereas rules are applied in their order (the rule with the lower number gets processed first) in Network ACL.
i.e. Security groups evaluate all the rules in them before allowing a traffic whereas NACLs do it in the number order, from top to bottom.
Defense order
Network ACL first layer of defense, whereas Security group is second layer of the defense for inbound/ingress traffic.
Security group first layer of defense, whereas Network ACL is second layer of the defense for outbound/egress traffic.
Occurrence
Subnet can have only one NACL, whereas Instance can have multiple Security groups.
I presented “What is Serverless computing?” in a recent public talk organized by https://www.letustalkit.com/letustalkit-webinars.
Internet is Mesh topology. read more to understand 😉
Star topology is singe point of failure, which mean all the devices are connected to hub connected as the center of star with single wire. If hub / switch fails network will go down.
Our home wifi works on wireless star topology, where in all cellphone/devices are connected to router as center of star.
In Mesh topology, one devices is connected with several other devices using multiple wires. (wire mesh). That way if one hub fails, network still works.
Mesh topology is opposite of single point of failure and is redundant, which means even if one router fails, data packet can be relayed or routed using different route or path. Imagine a big house with one in modem and router with multiple wifi extenders, that way if range is week for one extenders, data can still travel using other extender device to reach to modem 🙂
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