Troubleshooting

Question 1

EC2 Troubleshooting – Connectivity issues to an EC2 instance

Answer 1

Correct ports on the security group are may not be open.

Question 2

Cannot attach an EBS volume to an EC2 instance

Answer 2

EBS volumes must live in the same AZ as EC2 instance.

create a snapshot from volume and launch volume in the correct AZ.

Question 3

Cannot launch additional instances

Answer 3

probably reached the EC2 limit and need to contact AWS to increase limit.

Question 4

Unable to download package updates

Answer 4

EC2 may not have a public/EIP address, or desnot belong to a public subnet

Question 5

Applications seeming to slow down on T2 micro instances

Answer 5

t2 micro instances utilized CPU credits(for “burstable” processing). so chances are your application is using too much processing power and needs a larger instance or different instance type.

Question 6

AMI upavailable in other regions

Answer 6

AMI are only available in the regions that they are created.

an AMI can be copied to another region but will receive a new AMI id.

Question 7

Capacity error when attempting to launch an instance in a placement group

Answer 7

start and stop all the instances in the placement group(AWS tries to locate them as close as possible).

Question 8

New EC2 instances are not automatically being assigned a public IP address

Answer 8

auto-assign public IP setting on the subnet is checked.

Question 9

NAT gateway is configured but instances inside a private subnet still cannot download packages

Answer 9

Need to add 0.0.0.0/0 route to the NAT gateway on the route table for private subnets.

Question 10

Traffic is not making it to the instances even though security group rules are correct

Answer 10

check the NACL to ensure the proper ports from the proper sources are open(also check your IGW and route table settings).

Question 11

Error when attempting to attach multiple internet gateways to a VPC

Answer 11

Only one internet gateway can be attached to a VPC at any given time.

Question 12

error when attempting to attach multiple Virtual Private gateways to a VPC

Answer 12

only one virtual private gateway can be attached to a VPC at any given time.

Question 13

VPC Security group for EC2 instnace does not have enough rules for the required application

Answer 13

Assign the EC2 instance to multiple Security groups.

Question 14

Cannot SSH/communicate with resources inside of a private subnet.

Answer 14

not set up a VPN or not connected to Bastion host within the VPC to launch a connection from.

Question 15

Successful site to site VPN connection but unable to access extended resources

Answer 15

need to add on-premise routes to the Virtual Private Gateway route table

Question 16

Failure to create a VPC peering connection between two VPC’s in different regions

Answer 16

Previously peering connection has to between 2 VPC’s in the same region. But VPC can now be connected across regions.

Question 17

Load balancing is not occurring between instances in multiple availability zones

Answer 17

Make sure “Enable Cross-Zone load balancing” has been selected.

Question 18

Instances are healthy but are not registering as healthy with the ELB

Answer 18

Check configuration for the “health check” to make sure you have selected the proper ping protocol, ping port, and pig path.

Question 19

ELB is configured to listen on port 80, but traffic is not making it to the instances that belong to the ELB

Answer 19

may have mistaken the “Listener” for the security group. Listeners are not the same as the security group rules, port 80 still needs to be open on the security group that the ELB is using.

Question 20

Access logs on web servers show IP address of the E<b></b>

Answer 20

Enable Access Logs to Amazon s3.

Question 21

Unable to add instances from a specific subnet to the ELB

Answer 21

MOST LIKELY THE SUBNET THAT THE INSTANCE lives in has not been added to the ELBs configuration.

Question 22

Auto Scaled instance continues to start and stop in short intervals

Answer 22

scale-up and scale-down thresholds may be too close to each other. Either raise the scale-up or lower the scale-down thresholds.

Question 23

Auto scaling does not occur even though scaling policies are configured correctly

Answer 23

The “max” number of instances set in the auto scaling group may have been reached.

Question 24

If you are unable to download software packages to an EC2 instance, that means you have definitely provisioned it in a private subnet.

Answer 24

There can be many reasons why you cannot download software packages besides the instance being provisioned in a private subnet. For example, creating an instance without a public IP address or not having the proper ports open on the security group can cause issues downloading software.