Home > Articles > Cisco Certification > CCIE > CCIE Self-Study: Security Protocols

CCIE Self-Study: Security Protocols

  • Sample Chapter is provided courtesy of Cisco Press.
  • Date: Oct 28, 2005.

Chapter Description

This chapter covers some of today's most widely used technologies that enable network administrators to ensure that sensitive data is secure from unauthorized sources. Standards such as IP Security (IPSec) and encryption standards are covered, as are all the fundamental foundation topics you need to understand to master the topics covered in the CCIE Security written exam.

Foundation Topics

Authentication, Authorization, and Accounting

Authentication, authorization, and accounting (AAA, pronounced triple A) provides security to Cisco IOS routers and network devices beyond the simple user authentication available on IOS devices.

AAA provides a method to identify which users are logged into a router and each user's authority level. AAA also provides the capability to monitor user activity and provide accounting information.

In today's IP networks, access to network data is available in a variety of methods, including the following:

  • PSTN dialup modems
  • ISDN dialup
  • Internet access through virtual private networks (VPNs)

The AAA model is defined as follows:

  • Authentication— Who are you?
  • Authorization— What resources are you permitted to use?
  • Accounting— What resources were accessed, at what time, by whom, and what commands were issued?

The three phases ensure that legitimate users are permitted access. A remote user must be authenticated before being permitted access to network resources.

Authentication allows the user to submit a username and password and permits challenges and responses. After the user is authenticated, authorization defines what services or resources in the network users are permitted access to. The operations permitted here can include IOS-privileged EXEC commands. For example, a user might type commands but be permitted to use only certain show and debug commands for which the user is authorized.

Accounting allows the network administrator to log and view what was actually performed (for example, if a Cisco router was reloaded or the configuration was changed). Accounting ensures that an audit will enable network administrators to view what was performed and at what time it was performed. Accounting keeps track of the information needed to audit and report network resource usage. This typically includes the username, the start and stop time of login, and the commands typed by the user.

Figure 4-1 displays a typical secure network scenario.

04fig01.gif

Figure 4-1 Secure Network Access

The users could be dialup users running async (in this case, PSTN) or using ISDN with Point-to-Point Protocol (PPP). The network access server (NAS) ensures that only authenticated users have access to the secure network; it maintains resources and accounting information.

Authorization tells which resources, or host devices, are authorized to be accessed (such as FTP servers). The NAS implements the AAA protocols and also collects data regarding what network resources were accessed. The NAS can also ensure that devices in the secured network require authentication. For example, the users in Figure 4-1 who are accessing Router R1 require a valid username/password pairing to enter any IOS commands.

The following sections further define what authentication, authorization, and accounting are by discussing a common Cisco IOS router example.

Authentication

Authentication allows administrators to identify who can connect to a router by including the user's username and password. Normally, when a user connects to a router remotely by Telnet, the user must supply only a password, and the administrator has no way of knowing the user's username. You can, however, configure local usernames and passwords on a Cisco IOS router, but this does not scale well and it is not very secure. Configuring a small set of routers with individual usernames and passwords (IOS syntax username username password password) is fine, but doing so for large networks would be a difficult exercise to manage. Centrally locating the usernames and passwords is a better solution because only a few devices need to be updated and maintained. Also, users are not logged, and their configuration changes are not monitored without further configuration changes made on each individual router.

Example 4-1 displays a sample code snippet of a remote user accessing a AAA-configured Cisco router by Telnet.

Example 4-1. Username/Password Pair Entry

Sydney>telnet San-Fran
Trying san-fran (10.99.1.1)... Open User Access Verification
Username: drewrocks
Password: xxxxxxxx
San-Fran>

As you can see in Example 4-1, the user must enter a valid username and password to gain access to the router. Typically, a database containing the valid usernames resides locally on the router or on a remote security server.

Authorization

Authorization comes into play after authentication. Authorization allows administrators to control the level of access users have after they successfully gain access to the router. Cisco IOS allows certain access levels (called privilege levels) that control which IOS commands the user can issue. For example, a user with a privilege level of 0 cannot issue many IOS commands. There are five commands at privilege level 0: disable, enable, exit, help, and logout. A user with a privilege level of 15 can perform all valid IOS commands. The local database or remote security server can grant the required privilege levels.

Remote security servers, such as RADIUS and TACACS+, authorize users for specific rights by associating attribute-value (AV) pairs, which define those rights with the appropriate user. AAA authorization assembles a set of attributes that describes what the user is authorized to perform. These attributes are compared with the information contained in a database for a given user, and the result is returned to AAA to determine the user's actual permissions and restrictions.

The higher the privilege, the more capabilities a user has with the IOS command set.

Accounting

Accounting occurs after authentication and authorization have been completed. Accounting allows administrators to collect information about users. Specifically, administrators can track which user logged into which router, which IOS commands a user issued, and how many bytes were transferred during a user's session. For example, accounting enables administrators to monitor which routers have had their configurations changed. Accounting information can be collected by a remote security server.

To display local account information on a Cisco router collecting accounting information, issue the show accounting IOS command. Example 4-2 displays sample output when the command is issued on Router R1. (Note that for Cisco IOS 12.2T and higher, the command has changed to show aaa user all.)

Example 4-2. show accounting Command

R1#show accounting
Active Accounted actions on Interface Serial0:1, User jdoe Priv 1
 Task ID 15, Network Accounting record, 00:00:18 Elapsed
 task_id=15 timezone=PDT service=ppp mlp-links-max=4 mlp-links-current=4
protocol=ip addr=119.0.0.2 mlp-sess-id=1
      Overall Accounting Traffic
          Starts   Stops  Updates  Active  Drops
Exec           0       0        0       0       0
Network        8       4        0       4       0
Connect        0       0        0       0       0
Command        0       0        0       0       0
Rsrc-mgmt      1       0        0       1       0
System         0       0        0       0       0
 User creates:21, frees:9, Acctinfo mallocs:15, frees:6
Users freed with accounting unaccounted for:0
Queue length:0

Table 4-1 describes the fields contained in Example 4-2.

Table 4-1. show accounting Fields

Field

Description

User

The user's ID

Priv

The user's privilege level (0-15)

Task ID

Each accounting session's unique identifier

Accounting Record

Type of accounting session

Elapsed

Length of time (hh:mm:ss) for this session type

Rather than maintain a separate database with usernames, passwords, and privilege levels, you can use external security servers to run external security protocols—namely RADIUS and TACACS.

These security server protocols stop unauthorized access to your network. The following sections review these two security protocols.

3. Remote Authentication Dial-In User Service | Next Section Previous Section

Cisco Press Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from Cisco Press and its family of brands. I can unsubscribe at any time.

Overview

Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about Cisco Press products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites; develop new products and services; conduct educational research; and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@ciscopress.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security

Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children

This site is not directed to children under the age of 13.

Marketing

Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out

Users can always make an informed choice as to whether they should proceed with certain services offered by Cisco Press. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.ciscopress.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links

This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020