How Do You Create Peering Connections to EC-2 Instances, inside VPCs, So They Can Communicate with Each Other?

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Problem scenario
You want to use peering connections between two VPCs (in the same region) so that EC-2 instances in each VPC can communicate with each other. How do you do this?

Solution
Prerequisite
This assumes you have two VPCs already created in the same region. This assumes you have EC-2 instances also created.

i. Create one VPC.

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How Do You Connect to an EC-2 Instance in a VPC?

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Problem scenario
You cannot reach the public IP address of an EC-2 instance. You get “Network connection timed out” errors. The EC-2 instance is in a VPC. You have configured the relevant Network ACLs of the VPC and the EC-2 instance’s Security Groups to allow connectivity from your workstation. What could be wrong?

Solution

  1. Make sure you have an Internet Gateway that has been created and attached to the relevant VPC.

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How Do You Fix an A Record in Active Directory That Has Two Domain Names?

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Problem scenario
You added an A Record to DNS in Active Directory. You accidentally added the FQDN and the parent domain name was added. Now the A Record is too long and has a duplicative domain name like this:

server1.continualintegration.com.continualintegration.com

You tried modifying the FQDN in the A record, but it was immutable. What should you do?

Solution
Try waiting one hour.

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How Do You Troubleshoot “Connect timeout on endpoint https://ssm.us-west1.amazonaws.com…”?

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Problem scenario
You try to run an aws ssm command. But you get an error about a connection timing out. What should you do?

Solution
Find the EC-2 server’s VPC and subnet. Go to VPC in the AWS console. Go to the Subnet section. Find the Route Table associated with the subnet for the EC-2 server. Make sure that the “Destination” field accommodates the IP address of the ssm.us-west1.amazonaws.com hostname.

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How Do You Troubleshoot the Postfix Error “454 4.7.1 jdoe@acme.com: Relay access denied”?

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Problem scenario
You are trying to send an email on a Postfix server. But you keep getting this error: “454 4.7.1 jdoe@acme.com: Relay access denied”

What should you do?

Solution

  1. Back up the /etc/postfix/main.cf file just in case. (This is an optional step.)
  2. Find you server’s internal IP address with a command like this: ip addr show | grep eth0 | grep inet | awk ‘{print $2}’
  3. Modify the /etc/postfix/main.cf file.

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What Do You Do when Your Internet Speed Is Slow?

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Problem scenario
You are at home and your internet is slow. What should you do?

Possible solution #1
Reboot the cable router and any intermediate routers (i.e., any network device such as an IDS or firewall).

Possible solution #2
Log into your router’s interface to view the connected devices. To do this, find the default gateway IP address of your computer.

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How Do You Find the Underlying Component in AWS for a Given URL Endpoint?

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Problem scenario
You have been given a URL endpoint that is supported by some AWS service or services. How do you find out what the underlying service is?

Solution

  1. Determine the IP address. Ping the hostname. If you have a URL like this, https://acme.com/path/to/file.html, extract the domain name; you can deduce it is acme in the example. Open a command terminal and ping acme.

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