Chapter 2: Securing Network Devices

Chapter Outline:

2.0 Introduction
2.1 Securing Device Access
2.2 Assigning Administrative Roles
2.3 Monitoring and Managing Devices
2.4 Using Automated Security Features
2.5 Securing the Control Plane
2.6 Summary

Section 2.1: Securing Device Access

Upon completion of this section, you should be able to:

  • Explain how to secure a network perimeter.
  • Configure  secure administrative access to Cisco routers.
  • Configure enhanced security for virtual logins.
  • Configure an SSH daemon for secure remote management.

Topic 2.1.1: Securing the Edge Router

Securing the Network Infrastructure

Edge Router Security Approaches

Three Areas of Router Security

Secure Administrative Access

  • Tasks:
    • Restrict device accessibility
    • Log and account for all access
    • Authenticate access
    • Authorize actions
    • Present legal notification
    • Ensure the confidentiality of data

Secure Local and Remote Access

Topic 2.1.2: Configuring Secure Administrative Access

Strong Passwords

  • Guidelines:
    • Use a password length of 10 or more characters.
    • Include a mix of uppercase and lowercase letters, numbers, symbols, and spaces.
    • Avoid passwords based on easily identifiable pieces of information.
    • Deliberately misspell a password (Smith = Smyth = 5mYth).
    • Change passwords often.
    • Do not write passwords down and leave them in obvious places.

Increasing Access Security

Secret Password Algorithms


  • Configure all secret passwords using type 8 or type 9 passwords
  • Use the enable algorithm-type command syntax to enter an unencrypted password

  • Use the username name algorithm-type command to specify type 9 encryption

Securing Line Access

Topic 2.1.3: Configuring Enhanced Security for Virtual Logins

Enhancing the Login Process

Virtual login security enhancements:

  • Implement delays between successive login attempts
  • Enable login shutdown if DoS attacks are suspected
  • Generate system-logging messages for login detection

Configuring Login Enhancement Features

Enable Login Enhancements

Logging Failed Attempts

Topic 2.1.4: Configuring SSH

Steps for Configuring SSH

Example SSH Configuration

Example Verification of SSH

Modifying the SSH Configuration

Connecting to an SSH-Enabled Router

Two ways to connect:

  • Enable SSH and use a Cisco router as an SSH server or SSH client.
    • As a server, the router can accept SSH client connections
    • As a client, the router can connect via SSH to another SSH-enabled router
  • Use an SSH client running on a host, such as PuTTY, OpenSSH, or TeraTerm.

Section 2.2: Assigning Administrative Roles

Upon completion of this section, you should be able to:

  • Configure administrative privilege levels to control command availability.
  • Configure role-based CLI access to control command availability.

Topic 2.2.1: Configuring Privilege Levels

Limiting Command Availability

Privilege levels:

  • Level 0: Predefined for user-level access privileges.
  • Level 1: Default level for login with the router prompt.
  • Level 2-14: May be customized for user-level privileges.
  • Level 15: Reserved for the enable mode privileges.

Levels of access commands:

  • User EXEC mode (privilege level 1)
    • Lowest EXEC mode user privileges
    • Only user-level command available at the router> prompt
  • Privileged EXEC mode (privilege level 15)
    • All enable-level commands at the router# prompt

Privilege Level Syntax

Configuring and Assigning Privilege Levels

Limitations of Privilege Levels

  • No access control to specific interfaces, ports, logical interfaces, and slots on a router
  • Commands available at lower privilege levels are always executable at higher privilege levels
  • Commands specifically set at higher privilege levels are not available for lower privilege users
  • Assigning a command with multiple keywords allows access to all commands that use those

Topic 2.2.2: Configuring Role-Based CLI

Role-Based CLI Access

For example:

  • Security operator privileges
    • Configure AAA
    • Issue show commands
    • Configure firewall
    • Configure IDS/IPS
    • Configure NetFlow
  • WAN engineer privileges
    • Configure routing
    • Configure interfaces
    • Issue show commands

Role-Based Views

Configuring Role-Based Views

Step 1

Step 2

Step 3

Step 4

Configuring Role-Based CLI Superviews

Step 1

Step 2

Step 3

Verify Role-Based CLI Views

Enable Root View and Verify All Views

Section 2.3: Monitoring and Managing Devices

Upon completion of this section, you should be able to:

  • Use the Cisco IOS resilient configuration feature to secure the Cisco IOS image and configuration files.
  • Compare in-band and out-of band management access.
  • Configure syslog to log system events.
  • Configure secure SNMPv3 access using ACL
  • Configure NTP to enable accurate timestamping between all devices.

Topic 2.3.1: Securing Cisco IOS Image and Configuration Files

Cisco IOS Resilient Configuration Feature

Enabling the IOS Image Resilience Feature

The Primary Bootset Image

Configuring Secure Copy

Configure the router for server-side SCP with local AAA:

  1. Configure SSH
  2. Configure at least one user with privilege level 15
  3. Enable AAA
  4. Specify that the local database is to be used for authentication
  5. Configure command authorization
  6. Enable SCP server-side functionality

Recovering a Router Password

  1. Connect to the console port.
  2. Record the configuration register setting.
  3. Power cycle the router.
  4. Issue the break sequence.
  5. Change the default configuration register with the confreg 0x2142 command.
  6. Reboot the router.
  7. Press Ctrl-C to skip the initial setup procedure.
  8. Put the router into privileged EXEC mode.
  9. Copy the startup configuration to the running configuration.
  10. Verify the configuration.
  11. Change the enable secret password.
  12. Enable all interfaces.
  13. Change the config-register with the config-register configuration_register_setting.
  14. Save the configuration changes.

Password Recovery

Disable Password Recovery

No Service Password Recovery

Password Recovery Functionality is Disabled

Topic 2.3.2: Secure Management and Reporting

Determining the Type of Management Access

  • In-Band Management:
    • Apply only to devices that need to be managed or monitored
    • Use IPsec, SSH, or SSL when possible
    • Decide whether the management channel need to be open at all time

  • Out-of-Band (OOB) Management:
    • Provide highest level of security
    • Mitigate the risk of passing management protocols over the production network

Out-of-Band and In-Band Access

Topic 2.3.3: Using Syslog for Network Security

Introduction to Syslog

Syslog Operation

Syslog Message

Security Levels

Example Severity Levels

Syslog Systems

Configuring System Logging

Step 1

Step 2 (optional)

Step 3

Step 4

Topic 2.3.4: Using SNMP for Network Security

Introduction to SNMP

Management Information Base

SNMP Versions

SNMP Vulnerabilities


  • Transmissions from manager to agent may be authenticated to guarantee the identity of the sender and the integrity and timeliness of a message.
  • SNMPv3 messages may be encrypted to ensure privacy.
  • Agent may enforce access control to restrict each principal to certain actions on specific portions of data.

Configuring SNMPv3 Security

Secure SNMPv3 Configuration Example

Verifying the SNMPv3 Configuration

Topic 2.3.5: Using NTP

Network Time Protocol

NTP Server

Sample NTP Topology

Sample NTP Configuration on R1

Sample NTP Configuration on R2

NTP Authentication

Section 2.4: Using Automated Security Features

Topic 2.4.1: Performing a Security Audit

Discovery Protocols CDP and LLDP

Settings for Protocols and Services

  • There is a detailed list of security settings for protocols and services provided in Figure 2 of this page in the course.
  • Additional recommended practices to ensure a device is secure:
    • Disable unnecessary services and interfaces.
    • Disable and restrict commonly configured management services.
    • Disable probes and scans. Ensure terminal access security.
    • Disable gratuitous and proxy ARPs
    • Disable IP-directed broadcasts.

Topic 2.4.2: Locking Down a Router Using AutoSecure

Cisco AutoSecure

Using the Cisco AutoSecure Feature

Using the auto secure Command

  1. The auto secure command is entered
  2. Wizard gathers information about the outside interfaces
  3. AutoSecure secures the management plane by disabling unnecessary services
  4. AutoSecure prompts for a banner
  5. AutoSecure prompts for passwords and enables password and login features
  6. Interfaces are secured
  7. Forwarding plane is secured

Section 2.5: Securing the Control Plane

Topic 2.5.1: Routing Protocol Authentication

Routing Protocol Spoofing

Consequences of protocol spoofing:

  • Redirect traffic to create routing loops.
  • Redirect traffic so it can be monitored on an insecure link.
  • Redirect traffic to discard it.

OSPF MD5 Routing Protocol Authentication

OSPF SHA Routing Protocol Authentication

Topic 2.5.2: Control Plane Policing

Network Device Operations

Control and Management Plane Vulnerabilities

CoPP Operation

Section 2.6: Summary

Chapter Objectives:

  • Configure secure administrative access.
  • Configure command authorization using privilege levels and role-based CLI.
  • Implement the secure management and monitoring of network devices.
  • Use automated features to enable security on IOS-based routers.
  • Implement control plane security.

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