CCNP Quick notes

CoPP

Control Plane Policing (CoPP) is a network security feature used in Cisco devices and other network equipment to protect the control plane of the device. The control plane is responsible for managing and maintaining the device's routing and switching functions, it works like Brain of network device. Protecting the control plane is essential to ensure the stability and security of a network device.

Control Plane Policing is designed to prevent unauthorized or malicious traffic from overwhelming the control plane and causing network disruptions. It involves setting limits on the amount of traffic that the control plane can process, effectively creating a policing mechanism for control plane traffic. When traffic exceeds the configured limits, CoPP can either drop or rate-limit the excess traffic to protect the control plane.

Key components of Control Plane Policing include:

• Access Control Lists (ACLs): CoPP uses access control lists to define which types of traffic are allowed or denied access to the control plane. ACLs can be configured to match specific protocols, ports, or source/destination IP addresses.
• Rate Limiting: CoPP enforces rate limits on control plane traffic. This ensures that the control plane only processes a specific amount of traffic within a given time frame.
• Class Maps and Policy Maps: Control Plane Policing uses class maps and policy maps to define the traffic classification and policing actions. Class maps specify the criteria for identifying traffic, and policy maps define how the traffic is policed.
• Logging and Monitoring: CoPP typically provides logging and monitoring capabilities so that network administrators can track control plane traffic and any actions taken by the CoPP feature.

Difference between conform-action, exceed-action and violate-action in control plane policing

In Control Plane Policing (CoPP), "conform-action," "exceed-action," and "violate-action" are actions that specify what should happen to different types of traffic based on whether they conform to, exceed, or violate the configured traffic rate limits. These actions are used to control and manage traffic that is being policed by CoPP.

Here's an explanation of each of these actions:

• Conform-Action: This action is applied to traffic that conforms to the configured rate limits. In other words, when traffic falls within the permitted rate, it "conforms." The "conform-action" specifies what should happen to this traffic. Typically, conforming traffic is allowed to pass through without any additional restrictions. It's considered acceptable and within the defined policing parameters.
• Exceed-Action: This action is applied to traffic that exceeds the configured rate limits but doesn't violate them. When traffic exceeds the specified rate but is still within the defined excess rate, the "exceed-action" determines what should happen. Common actions for exceeding traffic include dropping it or remarking the traffic to a lower priority or a different class of service. The idea is to handle this traffic less favorably than conforming traffic but not as harshly as violating traffic.
• Violate-Action: This action is applied to traffic that violates the configured rate limits. When traffic exceeds the maximum rate allowed, it is considered a "violation." The "violate-action" specifies how to handle this traffic. Typically, violating traffic is either dropped or remarked to a lower priority or a different class of service. Violating traffic is generally the least desirable and may be associated with potential threats or attacks.

IPSLA

IPSLA, or Cisco IOS IP Service Level Agreements, is a feature in Cisco routers and switches that allows network administrators to measure, verify, and report on network performance.

ip sla 1 icmp-echo <target IP> frequency 60 exit

ip sla schedule 1 life forever start-time now

show ip sla statistics 1

EEM

Cisco Embedded Event Manager (EEM) is a powerful and flexible subsystem available on Cisco devices that allows you to monitor events and take automated actions in response. EEM provides a scripting language that allows you to define policies to respond to events on the device.

Basic Concepts:

1. Event: An event is a significant occurrence or a state change that can trigger an action. Events can be related to system-level changes, interface status, SNMP traps, syslog messages, etc.

2. Policy: A policy is a set of rules that define what action should be taken when a specific event occurs.

3. Action: An action is a task or command that is executed when a policy is triggered by an event.

Steps to Create a Basic EEM Script:

1. Enter EEM Configuration Mode:

enable

configure terminal

event manager applet <applet_name>

Define the Event:

event <event_type> <event_name>

Specify the Action:

action <action_type> <action_command>

Exit Configuration Mode &

Save Configuration:

Example of EEM

enable configure terminal event manager applet InterfaceUpDown event syslog pattern "LINK-3-UPDOWN" occurs 1 action 1.0 syslog priority emergencies msg "Interface is down - taking action" exit write memory

Interview question on Cisco EEM?

1. What is Cisco EEM?

2. Answer: Cisco EEM, or Embedded Event Manager, is a feature embedded in Cisco devices that provides a scripting interface for monitoring events and taking automated actions in response to those events.

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4. What are the key components of an EEM policy?

5. Answer: An EEM policy consists of an event, a trigger that specifies when the policy should be executed, and an action, which defines the tasks or commands to be performed when the event occurs.

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7. Can you give an example of an event in EEM?

8. Answer: An example of an event is "event syslog pattern," where a policy is triggered based on a specific pattern in syslog messages.

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10. How do you create a basic EEM policy?

11. Answer: Use the event manager applet configuration mode, define an event using the event command, and specify actions using the action command.

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13. What is the purpose of the occurs keyword in an EEM policy?

14. Answer: The occurs keyword specifies how many times an event must occur before the associated actions are executed. For example, occurs 1 means the actions will be triggered on the first occurrence of the event.

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16. Explain the use of the poll-interval keyword in an SNMP-related EEM event.

17. Answer: The poll-interval keyword sets the interval at which an SNMP query is repeated. It defines how often the device checks the specified SNMP variable for changes.

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19. How can you view the existing EEM policies on a Cisco device?

20. Answer: Use the show event manager policy registered command to view a list of registered EEM policies.

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22. What is the difference between an EEM applet and an EEM script?

23. Answer: An EEM applet is a simple and single-shot policy, while an EEM script is a more complex and reusable set of policies. An EEM script can contain multiple applets.

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25. Can you explain the importance of error handling in EEM policies?

26. Answer: Error handling is crucial to ensure the robustness of EEM policies. Proper error handling helps prevent unintended consequences and ensures that the device behaves predictably even in the face of unexpected conditions.

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28. How do you troubleshoot EEM policies that are not working as expected?

29. Answer: Use the show event manager policy registered and show event manager policy registered detail commands to check the status and details of registered policies. Additionally, examine the syslog messages for any errors or debug EEM events using the debug event manager action cli command.

NetFlow

NetFlow is a network protocol developed by Cisco Systems for collecting IP traffic information and monitoring network traffic flow. It provides a way to collect and analyze data about the traffic flowing through a router or switch, allowing network administrators to gain insights into network utilization, identify performance issues, and enhance security. NetFlow is widely used in various network environments, including enterprise networks, service provider networks, and data centers.

Here are the key concepts and components of NetFlow:

1. Flow: In NetFlow, a flow is a unidirectional sequence of packets that share common characteristics. It include source and destination IP addresses, source and destination port numbers, protocol, and the type of service. The flow is the basic unit of measurement in NetFlow.

2. Flow Record: A flow record is a collection of key fields that define a flow. It include source and destination IP addresses, source and destination port numbers, protocol, and other relevant information. Flow records are used to store information about individual flows.

3. Flow Exporter: A flow exporter is responsible for aggregating flow records and exporting them to a NetFlow collector for further analysis. The exporter formats the flow records and sends them to the collector using the NetFlow protocol (typically UDP).

4. Flow Collector: The flow collector is a system or software that receives and stores the flow records sent by flow exporters. It is responsible for processing and analyzing the collected data. NetFlow collectors can provide insights into network traffic patterns, usage, and potential issues.

5. Flow Sampler: In some cases, not all packets are included in the NetFlow data to reduce the processing load on routers and switches. Flow samplers are mechanisms used to sample a subset of packets to estimate the characteristics of the entire flow.

6. NetFlow Versions: There are different versions of the NetFlow protocol, such as NetFlow v5, v9, and IPFIX (which is similar to NetFlow v9 and standardized by the IETF). Each version may have additional features and improvements over the previous ones.

Netflow configuration example:

# Enable NetFlow on an interface

interface GigabitEthernet0/0

  ip flow ingress

# Configure the NetFlow exporter

ip flow-export destination <collector-ip> <collector-port>

ip flow-export version 9