| Overview

The first module provided an overview of network security concepts, common vulnerabilities, attack methods, and the importance of a security policy. This module will focus on some of the tools that are available to network administrators to protect network traffic. Administrators can control access to the router, switch, and the network by managing access at the console ports and terminal lines, as well as setting up passwords, accounts, and privilege levels.

Routers and switches can support a large number of network services that allow users and host processes to connect to the network. Some of these services can be restricted or disabled, improving security without affecting the operational use of the network. For security purposes, it should be a common practice for network devices to only support the traffic and protocols the network needs.

In addition to disabling certain network services in the interest of greater security, administrators can also filter packets using Access Control Lists (ACLs) on inbound and outbound traffic. By carefully constructing ACLs, it is possible for a network administrator to reduce many types of network threats.

At the perimeter of a network, the router is often the first line of defense. One of the primary security measures here involves hiding internal network IP addresses from the external access so that information about the network topology and design is not compromised. Network Address Translation (NAT) can hide these addresses, which makes it more difficult for a potential attacker to gain an understanding of the network architecture and to subsequently exploit it.

This module also covers methods used to secure routing protocols and describes steps that can be taken to counteract various access and denial of service threats.

Once certain measures of protection have been implemented at the perimeter router, careful management and thorough audits of router operations are also necessary to reduce network downtime, improve security, and aid in the analysis of suspected security breaches. Event logging, authoritative time source processes, and adequate software and configuration maintenance are examples of network management tasks.

In addition to a general overview of router and switch security issues, this module also provides hands-on labs for essential skills such as configuring privileges and accounts, disabling and controlling TCP/IP services, and configuring routing protocol authentication, NTP, logging, and Secure Shell (SSH).

NOTE: It is required that the student study the commands covered in the chapter using the labs and the command reference. Not all required commands are covered in sufficient detail in the text alone. Successful completion of this course requires a thorough knowledge of command syntax and application.