The “Route Table Changes Alarm” is an AWS CloudWatch alarm that is triggered when a change is made to a route table in your AWS account. To remediate this misconfiguration, you can follow the steps below using AWS CLI:

1. Log in to your AWS account and open the AWS CLI.

2. Check the current status of the alarm by running the following command:

   aws cloudwatch describe-alarms --alarm-names <alarm-name>
   

   Replace <alarm-name> with the name of your Route Table Changes Alarm.

3. If the alarm is in the “ALARM” state, it means that a change has been made to a route table. To remediate this, you need to identify the change that was made and revert it.

4. To identify the change, you can check the CloudTrail logs for the time period when the alarm was triggered. Run the following command to get the CloudTrail events for the specified time period:

   aws cloudtrail lookup-events --start-time <start-time> --end-time <end-time> --lookup-attributes AttributeKey=EventName,AttributeValue=CreateRouteTable
   

   Replace <start-time> and <end-time> with the start and end time of the period when the alarm was triggered.

5. Review the CloudTrail events to identify the change that was made to the route table. Once you have identified the change, you can revert it by running the appropriate AWS CLI command.

   For example, if a new route was added to the route table, you can remove it by running the following command:

   aws ec2 delete-route --route-table-id <route-table-id> --destination-cidr-block <destination-cidr-block>
   

   Replace <route-table-id> with the ID of the affected route table and <destination-cidr-block> with the destination CIDR block of the route that was added.

6. After you have reverted the change, check the status of the alarm again to ensure that it is no longer in the “ALARM” state:

   aws cloudwatch describe-alarms --alarm-names <alarm-name>
   

   If the alarm is still in the “ALARM” state, repeat the above steps to identify and remediate any remaining misconfigurations.

Here are the step-by-step instructions to remediate the “Route Table Changes Alarm” misconfiguration in AWS using Python:

1. First, we need to identify the root cause of the alarm. Check the CloudWatch alarm to see which route table has been modified and by whom.

2. Once you have identified the route table that has been modified, you can revert the changes by updating the route table to its previous state. To do this, you will need to fetch the previous state of the route table.

3. To fetch the previous state of the route table, you can use the AWS CloudTrail service. CloudTrail logs all API calls made to your AWS account, including changes to route tables. You can use the boto3 library in Python to interact with the CloudTrail service.

4. Use the boto3 library to create a CloudTrail client and fetch the events related to the modified route table. You can use the following code snippet to fetch the events:

import boto3

client = boto3.client('cloudtrail')

response = client.lookup_events(
    LookupAttributes=[
        {
            'AttributeKey': 'ResourceName',
            'AttributeValue': '<route_table_id>'
        },
        {
            'AttributeKey': 'EventName',
            'AttributeValue': 'ModifyRouteTable'
        }
    ]
)

events = response['Events']

Replace <route_table_id> with the ID of the modified route table.

5. Once you have fetched the events, you can extract the previous state of the route table from the CloudTrail event. The previous state of the route table is stored in the previousState field of the resourceProperties object in the CloudTrail event.

6. Use the boto3 library to update the route table with its previous state. You can use the following code snippet to update the route table:

import boto3

client = boto3.client('ec2')

response = client.replace_route_table_association(
    AssociationId='<association_id>',
    RouteTableId='<route_table_id>'
)

print(response)

Replace <association_id> with the ID of the route table association, and <route_table_id> with the ID of the modified route table.

7. Finally, you can confirm that the route table has been updated to its previous state by checking the AWS Management Console or by using the boto3 library to fetch the route table details.

That’s it! By following these steps, you can remediate the “Route Table Changes Alarm” misconfiguration in AWS using Python.