Troubleshooting


1. Troubleshooting Methodology and Security Scenarios



1. Problem

  1. Identifying the Problem

    • How to recognize the presence of a problem:

      • Sources of problem identification: user complaints, log file entries, dashboards, and alerts.

      • Expanding analysis to encompass all relevant channels.

      • Decision-making: performing backups if necessary.

  2. Establishing a Theory of Probable Cause

    • Factors involved in formulating a probable cause theory:

      • Analyzing change management history.

      • Starting with simple and obvious causes.

      • Gathering information from users and staff.

      • Checking for commonality across multiple inputs.

      • Understanding the potential scope or blast radius of the issue.

  3. Testing the Theory

    • Developing and executing tests to validate the probable cause theory:

      • Creating one or more tests for verification.

      • Executing the tests to confirm or discard the theory.

  4. Confirmation or Iteration

    • Outcome after testing the theory:

      • Confirming the theory and proceeding with the determined problem and solution.

      • Discarding the theory and generating a new probable cause theory for further testing.

Tasks and their Associated Business Continuity Terms:

  1. Determine Downtime Requirement

    • Associated with RTO (Recovery Time Objective) and MTTR (Mean Time to Recovery).

  2. Restore Data from Backups

    • Associated with RPO (Recovery Point Objective).

  3. Re-provision Infrastructure

    • Associated with Infrastructure as Code templates.

  4. Provide Notifications to End Users

    • Requires a notification chart.

  5. Document Mitigation Steps

    • Refers to consulting playbooks for documentation.

2. Solution :

Implementation of Plan of Action:

  • Check Playbook Steps:

    • Verify steps and identify external dependencies.

  • Perform Playbook Steps:

    • Execute each step and validate for problem resolution or complications.

  • Validation and Iteration:

    • If the problem persists, revisit probable cause theory.

Verify Full System Functionality:

  • Perform Rigorous Testing:

    • Functional tests, regression tests, and optional performance tests to ensure system integrity.

Implement Preventative Guardrails:

  • Temporary Fixes:

    • Temporary measures with permission changes or virtual patches on WAF.

  • Long-term Solutions:

    • Consider code changes for a comprehensive and permanent resolution.

Root Cause Analysis:

  • Examine Evidence:

    • Analyze user feedback, logs, dashboards, and alerts to identify the root cause.

Documentation and Future Improvements:

  • Comprehensive Documentation:

    • Record symptoms, research, steps, and results in a ticketing system or suitable documentation tool.

  • Future Improvement Suggestions:

    • Utilize the documentation to propose enhancements and prevent similar issues in the future.

2) Security Permissions Issues

Types of Symptoms and Probable Causes

  • Understanding symptom types and choosing the correct direction:

    • Immediate probable cause recognition.

    • Next steps for eliminating incorrect probable causes.

Symptom Scenarios and Probable Causes:

  1. User Cannot Access a Resource:

    • Probable Causes:

      • Incorrect group membership.

      • Incorrect permissions for the resource.

      • Inactive subscription for SaaS offering.

  2. Administrator Unable to Access Virtual Machine with Elevated Privileges:

    • Probable Causes:

      • Missing or misconfigured admin role mapping.

      • Limited role permissions not allowing administrative login.

      • Issues with administrative password or run-as privileges.

  3. Administrator Cannot Assume Elevated Permissions:

    • Probable Causes:

      • Missing sudo permissions in Linux.

      • Lack of run-as privileges in Windows.

      • Typing or incorrect administrative password.

  4. User Cannot SSH to a Remote Linux Virtual Machine:

    • Probable Causes:

      • Missing SSH key pair.

      • Mismatch between public and private keys.

      • Incorrect key pair file permissions.

  5. Basic Authentication Failure:

    • Probable Causes:

      • Disabled user account.

      • Incorrect password.

      • Login attempted outside acceptable times.

  6. Multifactor Authentication (MFA) Failure:

    • Probable Causes:

      • Expired or incorrectly entered certificate/token.

      • Incorrectly configured biometrics.

      • Issues with smart card validity.

  7. Cloud Console/Dashboard Access Failure:

    • Probable Causes:

      • Group membership issues.

      • Role assignment problems.

      • Inactive subscription.

  8. User Unable to Access Infrastructure as a Service Resources:

    • Probable Causes:

      • IAM policy misconfiguration.

      • Incorrect administrative permissions.

      • Hypervisor administrative permission problems.

  9. Issues with Platform as a Service (PaaS) Access:

    • Probable Causes:

      • IAM permissions misconfiguration.

      • User access limits or quotas reached.

      • Firewall/filter blocking access.

  10. Challenges with Software as a Service (SaaS) Access:

    • Probable Causes:

      • Subscription-related issues.

      • Permissions (group or role) problems.

  11. Certificate Error in Web Browsing:

    • Probable Causes:

      • Expired or revoked certificate.

      • Untrusted certificate authority.

  12. MFA Certificate Error:

    • Probable Causes:

      • Expired or revoked certificate.

      • Smart card damage or malfunction.

  13. SSH-Based Connection Errors:

    • Probable Causes:

      • Missing or mismatched keys.

      • Unsupported key pair type.

      • Disabled key-based authentication on the remote system.


3) Troubleshooting Data Security Issues

  • Data security issues often trigger incident response plans.

Scenario 1: Intellectual Property Exposure:

  • Potential Causes:

    • Inadequate data loss prevention measures.

    • Uncovered new data.

    • Unencrypted data transfer.

    • Unencrypted data at rest.

    • Improper access control.

Scenario 2: PII Exposure (Personally Identifiable Information):

  • Potential Causes:

    • Misconfigured data loss prevention.

    • Unencrypted data in transit or at rest.

    • Inadequate access control.

Scenario 3: Data Exfiltration:

  • Potential Causes:

    • Data not adequately encrypted (in transit or at rest).

    • Missing or misconfigured access controls.

    • Incorrect classification of sensitive data.

Scenario 4: Unencrypted Data During Transit:

  • Potential Causes:

    • Failure to disable HTTP connections.

    • Failure to enforce HTTPS redirection.

    • Allowing insecure protocols (e.g., FTP, Telnet).

    • Incorrectly utilizing TCP instead of TLS at layer four.


4) Troubleshooting Networking Technologies

  • Comprehensive coverage of networking technologies in the certification.

Scenario 1: Cannot Access Instance or Subnet (AWS Example):

  • Troubleshooting Steps:

    • Check inbound security group rules for the instance.

    • Check inbound and outbound network ACLs for the subnet.

    • Understand statefulness for appropriate validation, Statefull firewalls you only need to validate one direction (Sg)

Scenario 2: Configuration Management Issues:

  • Potential Causes:

    • Configuration applied to incorrect resources.

    • Server resources in the wrong configuration group.

    • Syntax errors or typos in the configuration.

Scenario 3: Unreachable API Endpoint:

  • Troubleshooting Steps:

    • Validate credentials.

    • Confirm endpoint details.

    • Check rate limits or quotas.

    • Review access policy and firewall configurations.

Scenario 4: Intrusion Detection or Prevention Problems:

  • Challenges:

    • False positives.

    • False negatives.

Scenario 5: Web Application Firewall (WAF) Issues:

  • Potential Problems:

    • Improper traffic control.

    • Incorrect placement or misconfigured rules.

    • Issues with virtual patching.

Scenario 6: Unsupported Protocols:

  • Potential Causes:

    • Legacy applications using outdated protocols.

    • Unexpected clear text communication.

Scenario 7: DDoS Attack Experience:

  • Response Steps:

    • Activate the notification chart.

    • Implement short-term mitigation through WAF and firewalls.

    • Notify the cloud service provider or internet provider for assistance.


2. Deployment and Connectivity Scenarios


1) Configuration Issues


Infrastructure as Code (IaC) vs. Configuration Management (CM)

  • IaC: Focuses on provisioning and modifying fundamental virtual machine parameters (e.g., virtual CPUs).

  • CM: Encompasses operations within the operating system post-provisioning.

Potential Problems and Causes

  • Instance Deployment Failure:

    • Human involvement without automation increases inherent risks of errors or failure.

  • Modification Post-Provisioning:

    • Wrong script execution or misconfiguration of templates in IaC.

  • Incorrect Resource Modification:

    • Misapplied template during resizing, possibly resulting in incorrect instance size.

  • Tag or Label Errors:

    • Incorrectly assigned tags or labels causing erroneous task executions.

  • Automation Framework Issues:

    • Non-functional or incorrectly configured automation frameworks.

Applying Issues to Container Deployment

  • Container Image Issues:

    • Commonly stem from invalid or incorrect container images.

  • Container Engine Problems:

    • Container engine may not be running on the underlying compute resource.

  • Container Runtime Issues:

    • Container may not be running or may have failed.

  • Resource Overutilization:

    • Container demands more resources than physically available, causing deployment issues.


Network Latency Issues

  • Elevated latency between deployment server and target resource can cause deployment failure.

Auto-Scaling Configuration Errors

  • Incorrect parameters in auto-scaling configurations can lead to provisioning more resources than available capacity.

Public Cloud Limitations

  • Public cloud providers may lack the capacity required for auto-scaling, causing deployment failure.

Insufficient Server Capacity

  • Lack of virtual CPU or thread capacity can impede virtual machine launches.

Oversubscription Thresholds

  • Oversubscription may exceed configured limits, causing deployment failures.

Resource Scarcity

  • Insufficient memory, storage space, or throughput/IOPS can lead to deployment issues.

Network Bandwidth Limitations

  • Inadequate network bandwidth on a server can hinder task execution.

Template and Configuration Errors

  • IaC Template Issues:

    • Typos, syntax errors, or incorrect parameter values in the template.

  • Container Configuration Problems:

    • Incorrect container image, CPU, or memory requirements causing deployment failures.


Unavailable Tech Support

  • Root Causes:

    • Issue outside documented SLA boundaries.

    • Licensing problem not covering the level of support demanded.

Service Unavailability

  • Root Causes:

    • Service downtime within acceptable SLA boundaries.

    • Licensing issues, restricting access.

    • Exceeding usage limits, affecting certain users.

Licensing Problems

  • Root Causes:

    • Late or unpaid bills resulting in non-functioning software.

    • Installation outside licensing limits, preventing product functionality.

Billing and Payment Challenges

  • Root Causes:

    • Orphaned resources resulting in continued charges.

    • Unexpected usage spikes causing billing issues.

    • Invalid payment information or unpaid/late bills.


Failed Migration and Integration Problems

Unsupported Application for Migration

  • Root Causes:

    • Application not supported or too old for the cloud service provider.

Failed Migration Prerequisites

  • Root Causes:

    • Failure to meet migration prerequisites (e.g., OS version, data size).

Misconfigured Migration Automation

  • Root Causes:

    • Misconfiguration of migration automation, hindering the process.

Incompatibility Issues

  • Root Causes:

    • Incompatible OS versions between source and destination.

    • Migration automation requiring SSH or remote desktop, not enabled due to firewalling.

Neglected Due Diligence

  • Root Causes:

    • Lack of comprehensive due diligence, leading to unsupported application migration.

Database Compatibility Problems

  • Root Causes:

    • Incompatible database engines between source and destination, rendering migration impossible.

5) Network Troubleshooting Scenarios and Root Causes


Simple Network Troubleshooting Scenarios

**Scenario 1: Nodes in the Same Availability Zone and and on same Subnet with same Sg applied **

  • Potential Root Causes:

    • Security group issues (likely cause).

    • Network ACLs (only applied at subnet boundaries).

    • Route tables.

Scenario 2: Node B Moved to a Different Availability Zone and Subnet

  • Potential Root Causes:

    • Security group issues (likely cause).

    • Network ACLs.

    • Route tables (both potential root causes now).

Scenario 3: Node B Moved to a Different VPC

  • Potential Root Causes:

    • Security group issues.

    • Network ACLs.

    • Route tables.

Scenario 4: Node B in a Corporate Data Center

  • Potential Root Causes:

    • Security group issues.

    • Network ACLs.

    • Route tables.

    • On-premises networking equipment.

Complex Network Troubleshooting Scenario

Bastion Host and SSH Issue

  • Infrastructure Diagram:

    • VPC with public and private subnets.

    • Site-to-site VPN to corporate data center.

  • Troubleshooting Steps:

    • Check route tables (correct in both directions for SSH to Bastion host).

    • Verify Bastion host security group and public subnet network ACLs.

    • Check destination host security group and private subnet network ACLs.

  • Tools for Analysis:

    • AWS CloudTrail audit logs.

    • AWS Config for configuration history.

    • Enable VPC flow logs to analyze traffic flow.

  • Flow Log Analysis:

    • Analyze logs, confirm outbound network ACL rules issue in the destination subnet.

IP Address and Route Troubleshooting

Incorrect IP Address or Subnet Misconfiguration

  • Potential Causes:

    • Incorrect IP address.

    • Wrong subnet mask.

    • DHCP misconfiguration.

    • Failed DHCP attempt leading to a 169.254 address.

Incorrect Routes

  • Potential Causes:

    • Incorrect routes from DHCP.

    • Typoed static routes.

    • Incorrect dynamic routing (e.g., BGP) propagating wrong routes.


6) Troubleshooting Network Services: Scenarios and Root Causes

Load Balancer Troubleshooting

Web Asset Retrieval Issues

  • Potential Root Causes:

    • HTTPS listener used, but client attempts HTTP.

    • Mismatched encryption algorithms (e.g., TLS versions).

    • Missing or incorrect headers from the client.

    • Insufficient resources on the backend.

    • Configuration leading to a 500 response code.

Network Time Protocol (NTP) Troubleshooting

NTP Functionality Problems

  • Potential Root Causes:

    • Missing or incorrect local NTP configuration files.

    • Time drift between guest VM and host OS/hypervisor.

    • Unreachable NTP server or incorrectly configured NTS certs.

    • Time drift between NTP client and server.

    • NTP server unavailability.

DNS Troubleshooting

DNS Resolution Issues

  • Potential Root Causes:

    • Misconfigured local DNS settings.

    • Unreachable DNS server via the network.

    • DNS server outage or unavailability.

    • DNS server unable to serve records for the requested domain.

    • Misconfigured or missing individual records within a zone.


7) Commonly Used Network Troubleshooting Tools

1. Ping

  • Purpose: Determines if a packet can be delivered to the destination host and returned.

  • Symptoms:

    • Hangs or times out: Destination down or blocked by a firewall.

    • "Destination host unreachable": Network configuration on source host prevents reachability.

2. TraceRoute (Linux) / TraceRt.exe (Windows)

  • Purpose: Determines the network path packets take to reach a destination.

  • Usage: traceroute <hostname or IP> (Linux) or tracert <hostname or IP> (Windows).

3. nslookup

  • Purpose: Translates hostnames to IP addresses and validates DNS reachability.

  • Usage: nslookup <hostname> (can also ping a hostname for nslookup).

4. route

  • Purpose: Displays and manages local routes on both Linux and Windows.

5. ARP (Address Resolution Protocol)

  • Purpose: Views the local cache of MAC addresses and their association with IP addresses.

6. curl / wget

  • Purpose: Operates at the application layer (Layer 7) to test website connectivity and download files.

  • Usage: curl <URL> or wget <URL>.

7. Packet Capturing (Wireshark / TCPdump)

  • Purpose: Captures and analyzes network traffic, including packet contents.

  • Considerations: In public clouds like AWS, this type of traffic may be blocked.

    • Options include configuring packet mirroring, using a gateway load balancer, or forwarding traffic to backend appliances.

8. OpenSSL

  • Purpose: Inspects SSL and TLS certificates, verifies SSL connections.

  • Usage: Various commands, e.g., openssl s_client -connect <host>:<port> for SSL connection verification.

These tools help IT professionals troubleshoot network issues and identify root causes across different layers of the OSI model.


3. Performance and Automation Scenarios


1) Resource Utilization Issues

CPU Utilization

Overutilization

  • Symptoms:

    • High CPU usage indicated in OS commands, hypervisor graphs, or monitoring tools.

  • Recommendation: Optimize code, optimize applications, scale horizontally, or upgrade CPU.

Underutilization

  • Symptoms:

    • Low CPU usage despite sufficient load.

  • Recommendation: Optimize code, load balance, or scale vertically by upgrading CPU.

GPU Utilization

Overutilization

  • Symptoms:

    • High GPU usage; possible slow response or system lag.

  • Recommendation: Switch to a pass-through GPU.

Underutilization

  • Symptoms:

    • Low GPU usage; resources not efficiently utilized.

  • Recommendation: Switch to a shared GPU.

Memory Utilization

Overallocation

  • Symptoms:

    • Excess memory allocated, potentially indicated by hypervisor or third-party tools.

  • Recommendation: Downsize the VM, optimize memory allocation.

Underallocation

  • Symptoms:

    • Running out of memory.

  • Recommendation: Upsize the VM, allocate more memory (vertical scaling).

Storage Utilization

I/O Overutilization

  • Symptoms:

    • High storage I/O load.

  • Recommendation: Increase storage IOPS, optimize I/O.

I/O Underutilization

  • Symptoms:

    • Low storage I/O usage, potential inefficiency.

  • Recommendation: Decrease IOPS, switch to HDD storage if appropriate.

Capacity Overutilization

  • Symptoms:

    • Running out of disk space.

  • Recommendation: Increase volume size, optimize data storage.

Capacity Underutilization

  • Symptoms:

    • Provisioned space not fully utilized.

  • Recommendation: Decrease volume size to save costs.

Networking

Bandwidth Insufficiency

  • Symptoms:

    • Application slowness, connectivity issues.

  • Recommendation: Upsize the virtual machine or server.

Latency Issues

  • Symptoms:

    • High latency impacting application performance.

  • Recommendation: Optimize network configuration, monitor hardware resources, optimize application.

Replication Failure

  • Symptoms:

    • Database replication issues.

  • Recommendation: Benchmark network bandwidth and latency, verify replication server resources, check for replication errors.

Scaling Challenges

  • Symptoms:

    • Scaling not improving KPIs.

  • Recommendation: Check auto-scaling configurations, adjust scaling limits, optimize application performance.


2) Troubleshooting Application Performance and Infrastructure

Initial Steps and Infrastructure Checks

  • CDN (Content Delivery Network) Configuration:

    • Check caching configuration and cache hit rate.

  • Load Balancers:

    • Ensure load balancers are available and monitor metrics to prevent threshold breaches.

  • Application Configuration:

    • Verify correct application configuration, especially on load balancers and compute resources.

  • Cloud Infrastructure:

    • Check the management console for any outage notices that might affect the application.

User and Access Verification

  • User Access:

    • Confirm users have appropriate access and subscriptions for the application, especially in platform or software as a service (PaaS/SaaS) scenarios.

Memory Management for Applications

  • Memory Usage Analysis:

    • Examine memory usage through application logs, OS logs, and virtual machine configuration.

  • Memory Allocation:

    • Ensure the virtual machine has sufficient memory allocated for the application runtime.

  • Process Monitoring:

    • Check for unexpected processes consuming excessive memory.

  • Memory Leak Prevention:

    • Verify the application is not suffering from a memory leak, a common cause of application performance problems.

3) Troubleshooting Automation and Orchestration

Troubleshooting scenarios related to automation and orchestration often involve identifying the root causes of task failures, workflow issues, or patch management problems. Here are some common troubleshooting scenarios and their potential root causes:

Authentication Issues in Automation

  • SSH Key Mismatch:

    • Authentication fails due to SSH key mismatch between the control node and managed nodes.

  • Key Updates Not Propagated:

    • Authentication problems arise when SSH keys are updated but not properly propagated.

  • Service Account Mapping Misconfiguration:

    • Authentication issues may occur due to misconfigured service account mappings.

Orchestration Workflow Problems

  • Incorrect Task Sequencing:

    • Workflow failures may result from incorrect task sequencing.

  • Task Swap:

    • Tasks are mistakenly swapped, causing workflow issues.

  • Partial Unavailability:

    • A partial system outage disrupts a single task, leading to workflow failure.

Control Node Communication Failures

  • DNS Issues:

    • Control node fails to reach managed nodes due to DNS outage or misconfiguration.

  • Incorrect Hostname:

    • Communication problems arise when managed nodes use incorrect hostnames.

  • IP Changes:

    • IP address changes on managed nodes require firewall rule adjustments.

  • DHCP Problems:

    • DHCP issues can affect managed node connectivity.

  • Firewall Configuration:

    • Firewall settings may block communication between control and managed nodes.

  • Network Segment Changes:

    • Managed nodes moved to a different network segment, becoming unreachable from the control node.

Automation Process Failures

  • Software Version Mismatch:

    • Control node and managed nodes run different software versions.

  • Configuration Management Tool Version:

    • Incorrect configuration management tool version leads to process failures.

  • Incorrect OS Task Deployment:

    • Running a task intended for a different operating system on a node causes failures.

Deprecated Features

  • Deprecated Tool Versions:

    • Troubles arise when using deprecated versions of configuration management tools.

  • Newer OS Version:

    • Managed nodes run newer operating system versions than the control node.

  • Deprecated Settings Deployment:

    • Attempting to deploy deprecated settings leads to failures.

Automation Task Completion Issues

  • Task Never Started:

    • Tasks cannot complete if they never start; check automation logs for details.

  • Failed Tasks:

    • Individual tasks fail within the automation process; review logs to identify failures.

  • Dashboard Insights:

    • Utilize the orchestration software's dashboard to track completed tasks and identify issues.

Patch Management Failures

  • Disk Issues:

    • Disk problems prevent patches from being installed.

  • Incompatible Patch:

    • Patch is incompatible with the operating system or underlying hardware.

  • Network or Antivirus Interference:

    • Network components or antivirus software may block patch installation.

Troubleshooting these scenarios involves examining logs, verifying configurations, and identifying the specific issues causing automation or orchestration failures.