10 Cisco Application Centric Infrastructure Interview Questions and Answers

Cisco Application Centric Infrastructure (ACI) is a cutting-edge networking solution that revolutionizes how data centers are managed and operated. By integrating software-defined networking (SDN) principles, ACI provides a holistic approach to network automation, application agility, and centralized management. This technology is pivotal for organizations aiming to streamline their IT operations and enhance scalability while maintaining robust security protocols.

This article offers a curated selection of interview questions designed to test your knowledge and understanding of Cisco ACI. Reviewing these questions will help you gain a deeper insight into the core concepts and practical applications of ACI, ensuring you are well-prepared for any technical discussions or assessments.

Cisco Application Centric Infrastructure Interview Questions and Answers

1. Explain the role of the Application Policy Infrastructure Controller (APIC) in ACI.

The Application Policy Infrastructure Controller (APIC) is the centralized management and automation engine for Cisco’s Application Centric Infrastructure (ACI). It serves several key functions:

• Policy Management: APIC allows administrators to define and manage policies that dictate how applications interact with the network. These policies can be applied consistently across the entire network, ensuring uniform behavior.
• Network Automation: APIC automates the configuration and management of network devices, reducing the need for manual intervention. This automation helps in minimizing human errors and speeds up the deployment process.
• Centralized Control: APIC provides a single point of control for the entire ACI fabric. This centralized control simplifies the management of large-scale networks and makes it easier to implement changes.
• Visibility and Monitoring: APIC offers comprehensive visibility into the network’s performance and health. It provides real-time monitoring and analytics, helping administrators to quickly identify and resolve issues.
• Integration with Third-Party Tools: APIC supports integration with various third-party tools and applications, enabling a more flexible and extensible network management environment.

2. Write a Python script to create a new tenant using the REST API.

To create a new tenant in Cisco Application Centric Infrastructure (ACI) using the REST API, you need to follow these steps:

1. Authenticate with the APIC (Application Policy Infrastructure Controller).
2. Create the tenant using the appropriate API endpoint.
3. Handle the response to ensure the tenant was created successfully.

Here is a Python script that demonstrates these steps:

import requests
import json

# APIC credentials and URL
apic_url = "https://apic.example.com"
username = "admin"
password = "password"

# Authentication
auth_url = f"{apic_url}/api/aaaLogin.json"
auth_payload = {
    "aaaUser": {
        "attributes": {
            "name": username,
            "pwd": password
        }
    }
}

session = requests.Session()
response = session.post(auth_url, json=auth_payload, verify=False)
if response.status_code != 200:
    raise Exception("Authentication failed")

# Create tenant
tenant_name = "new_tenant"
tenant_url = f"{apic_url}/api/node/mo/uni/tn-{tenant_name}.json"
tenant_payload = {
    "fvTenant": {
        "attributes": {
            "name": tenant_name
        }
    }
}

response = session.post(tenant_url, json=tenant_payload, verify=False)
if response.status_code == 200:
    print("Tenant created successfully")
else:
    print("Failed to create tenant")

# Close the session
session.close()

3. What are End Point Groups (EPGs) and how do they function?

End Point Groups (EPGs) in Cisco Application Centric Infrastructure (ACI) are logical groupings of endpoints that require similar network and security policies. EPGs abstract the network configuration from the physical infrastructure, allowing for more flexible and scalable network management.

EPGs function by associating endpoints with a common set of policies, such as access control lists (ACLs), quality of service (QoS) settings, and other network policies. These policies are then applied uniformly to all endpoints within the EPG. This abstraction allows network administrators to manage policies at a higher level, reducing the complexity of managing individual endpoints.

In Cisco ACI, EPGs are typically associated with application profiles, which define the communication requirements between different EPGs. Contracts are used to specify the rules and policies that govern the interactions between EPGs. This model allows for a more modular and scalable approach to network policy management.

4. How would you use Ansible to automate the deployment of an ACI configuration? Provide a sample playbook.

Ansible is an open-source automation tool that simplifies the process of configuration management, application deployment, and task automation. When it comes to Cisco Application Centric Infrastructure (ACI), Ansible can be used to automate the deployment and management of ACI configurations. This is particularly useful for ensuring consistency, reducing manual errors, and speeding up the deployment process.

To automate the deployment of an ACI configuration using Ansible, you would typically use the Ansible ACI modules. These modules allow you to interact with the ACI fabric and perform various configuration tasks.

Here is a sample Ansible playbook to automate the deployment of an ACI configuration:

---
- name: Deploy ACI Configuration
  hosts: apic
  gather_facts: no
  tasks:
    - name: Create a tenant
      cisco.aci.aci_tenant:
        host: "{{ inventory_hostname }}"
        username: "{{ username }}"
        password: "{{ password }}"
        tenant: "example_tenant"
        description: "Example Tenant"
        state: present

    - name: Create an application profile
      cisco.aci.aci_ap:
        host: "{{ inventory_hostname }}"
        username: "{{ username }}"
        password: "{{ password }}"
        tenant: "example_tenant"
        app_profile: "example_app"
        description: "Example Application Profile"
        state: present

    - name: Create an EPG
      cisco.aci.aci_epg:
        host: "{{ inventory_hostname }}"
        username: "{{ username }}"
        password: "{{ password }}"
        tenant: "example_tenant"
        app_profile: "example_app"
        epg: "example_epg"
        description: "Example EPG"
        state: present

In this playbook:

• The aci_tenant module is used to create a tenant named “example_tenant”.
• The aci_ap module is used to create an application profile named “example_app” within the tenant.
• The aci_epg module is used to create an Endpoint Group (EPG) named “example_epg” within the application profile.

5. Write a script to retrieve all EPGs in a specific tenant using the REST API.

To retrieve all EPGs in a specific tenant using the Cisco ACI REST API, you need to follow these steps:

1. Authenticate with the Cisco ACI API.
2. Make a GET request to the appropriate endpoint to retrieve the EPGs.
3. Parse the response to extract the EPG information.

Here is a Python script that demonstrates this process:

import requests
import json

# Replace with your APIC IP, username, and password
apic_ip = "https://your-apic-ip"
username = "your-username"
password = "your-password"
tenant_name = "your-tenant-name"

# Authenticate and get the token
auth_url = f"{apic_ip}/api/aaaLogin.json"
auth_payload = {
    "aaaUser": {
        "attributes": {
            "name": username,
            "pwd": password
        }
    }
}
auth_response = requests.post(auth_url, json=auth_payload, verify=False)
auth_token = auth_response.json()["imdata"][0]["aaaLogin"]["attributes"]["token"]

# Set the headers with the token
headers = {
    "Cookie": f"APIC-cookie={auth_token}"
}

# Get the EPGs for the specified tenant
epg_url = f"{apic_ip}/api/node/class/fvAEPg.json?query-target-filter=eq(fvAEPg.dn,\"uni/tn-{tenant_name}\")"
epg_response = requests.get(epg_url, headers=headers, verify=False)
epgs = epg_response.json()["imdata"]

# Print the EPGs
for epg in epgs:
    print(epg["fvAEPg"]["attributes"]["dn"])

6. What are Contracts and how do they control traffic between EPGs?

In Cisco Application Centric Infrastructure (ACI), Contracts are used to define the rules and policies that control the communication between Endpoint Groups (EPGs). EPGs are logical groupings of endpoints, such as virtual machines or physical servers, that share common policy requirements.

Contracts consist of two main components: Subjects and Filters. Subjects define the types of traffic that are allowed or denied between EPGs, while Filters specify the exact criteria for the traffic, such as protocols and ports.

When an EPG wants to communicate with another EPG, a Contract must be established between them. This Contract specifies what type of traffic is permitted and under what conditions. Without a Contract, no communication is allowed between the EPGs, ensuring a secure and controlled environment.

7. Describe the steps to troubleshoot a connectivity issue between two EPGs.

To troubleshoot a connectivity issue between two Endpoint Groups (EPGs) in Cisco Application Centric Infrastructure (ACI), follow these steps:

1. Verify EPG Configuration: Ensure that both EPGs are correctly configured and associated with the appropriate Application Profile and Tenant. Check that the EPGs have the correct VLANs and are mapped to the correct physical or virtual domains.

2. Check Contracts: Verify that there are appropriate contracts in place between the EPGs. Contracts define the communication rules between EPGs, including filters and actions. Ensure that the contract is correctly applied and that the filters allow the necessary traffic.

3. Inspect Endpoint Learning: Confirm that the endpoints within the EPGs are properly learned by the ACI fabric. You can check the endpoint table to see if the MAC addresses and IP addresses of the endpoints are correctly registered.

4. Review Policy Enforcement: Ensure that policy enforcement is correctly configured. This includes verifying that the correct policies are applied to the EPGs and that there are no misconfigurations that could block traffic.

5. Check Fabric Health: Examine the health of the ACI fabric. Look for any faults or issues that could affect connectivity. This includes checking the status of the leaf and spine switches, as well as the APIC controllers.

6. Use Troubleshooting Tools: Utilize ACI’s built-in troubleshooting tools such as traceroute, ping, and the ACI troubleshooting wizard. These tools can help identify where the connectivity issue is occurring within the fabric.

7. Review Logs and Events: Check the logs and events in the APIC to see if there are any error messages or alerts related to the EPGs or the fabric. This can provide clues about what might be causing the connectivity issue.

8. How does ACI handle multi-site deployments and what are the key considerations?

Cisco Application Centric Infrastructure (ACI) handles multi-site deployments through the use of the Multi-Site Orchestrator (MSO). MSO provides a centralized management platform that allows for the configuration, monitoring, and management of multiple ACI fabrics across different geographical locations. This enables organizations to extend their ACI policies and configurations consistently across multiple data centers.

Key considerations for ACI multi-site deployments include:

• Inter-Site Connectivity: Ensure robust and reliable connectivity between sites, typically using IP-based transport networks. This includes considerations for latency, bandwidth, and redundancy.
• Policy Consistency: Maintain consistent policies across all sites to ensure uniform security, compliance, and application performance. MSO helps in replicating and synchronizing policies across sites.
• Disaster Recovery: Plan for disaster recovery and business continuity by leveraging ACI’s capabilities to quickly reconfigure and reroute traffic in case of site failures.
• Scalability: Consider the scalability of the ACI deployment to accommodate future growth in terms of additional sites, devices, and applications.
• Security: Implement robust security measures to protect inter-site communication and ensure that policies are enforced consistently across all locations.
• Operational Complexity: Be aware of the increased operational complexity that comes with managing multiple sites and ensure that the IT team is adequately trained and equipped to handle it.

9. Explain the concept of micro-segmentation and how it enhances security.

Micro-segmentation in Cisco ACI refers to the practice of creating highly granular security zones within a data center. This is achieved by defining security policies at the level of individual workloads or applications, rather than at the broader network level. By doing so, micro-segmentation ensures that even if an attacker breaches one segment, they cannot easily move laterally to other parts of the network.

In Cisco ACI, micro-segmentation is implemented using Endpoint Groups (EPGs). EPGs allow administrators to group endpoints with similar security requirements and apply specific policies to them. These policies can include access controls, quality of service (QoS) settings, and other security measures. The use of EPGs enables dynamic and automated policy enforcement, which is important for maintaining security in highly dynamic environments.

Micro-segmentation enhances security in several ways:

• Granular Control: By segmenting the network at a granular level, administrators can apply precise security policies tailored to specific applications or workloads.
• Reduced Attack Surface: Limiting the scope of each segment reduces the potential impact of a security breach, as attackers cannot easily move laterally within the network.
• Improved Compliance: Micro-segmentation helps organizations meet regulatory requirements by ensuring that sensitive data is isolated and protected according to compliance standards.
• Dynamic Policy Enforcement: Cisco ACI’s automation capabilities allow for real-time policy adjustments, ensuring that security measures are always up-to-date and effective.

10. Explain Role-Based Access Control (RBAC).

Role-Based Access Control (RBAC) in Cisco Application Centric Infrastructure (ACI) is a security mechanism that assigns permissions to users based on their roles within an organization. This approach helps in managing and controlling access to network resources efficiently.

In Cisco ACI, RBAC is implemented through the following components:

• Roles: Define a set of permissions that determine what actions a user can perform. Examples include network administrator, security administrator, and read-only user.
• Users: Individual accounts that are assigned one or more roles. Each user inherits the permissions associated with their roles.
• Domains: Logical groupings of resources that users can access. Domains help in segmenting the network and applying RBAC policies more granularly.

By using RBAC, Cisco ACI ensures that users have access only to the resources they need to perform their job functions, thereby enhancing security and reducing the risk of unauthorized access.