Home > Articles > Cisco > CCIE

This chapter is from the book

Section 7: IOS and IP Features (10 Points)

  • R2 is sited in a shared data center; make the serial link back into R1 as secure as possible at Layer 2.

Did you think about IP Security (IPsec)? Well that is Layer 3; as is any form of access-list, you should realize that PPP is Layer 2 and this protocol has the capability to run CHAP over it, which makes the serial link very secure. PPP with CHAP over a serial link is just as happy as PPP over ISDN; the configuration is exactly the same. If you have configured this correctly as in Example 1-56 and Example 1-57, you have scored 2 points. Example 1-58 shows CHAP in action over the serial link.

Example 1-56 R1 Serial Line PPP CHAP Configuration

username disco password 0 cisco
!
interface Serial0/0
 ip address 10.90.90.2 255.255.255.240
 encapsulation ppp
 clockrate 2000000
 ppp authentication chap
 ppp chap hostname misco

Example 1-57 R2 Serial Line PPP CHAP Configuration

username misco password 0 cisco
!
interface Serial0/0
 ip address 10.90.90.1 255.255.255.240
 encapsulation ppp
 ppp authentication chap
 ppp chap hostname disco

Example 1-58 R1 debug ppp authentication Output

R1#debug ppp authentication
PPP authentication debugging is on
3d23h: Se0/0 PPP: Treating connection as a dedicated line
3d23h: %LINK-3-UPDOWN: Interface Serial0/0, changed state to up
3d23h: Se0/0 CHAP: Using alternate hostname misco
3d23h: Se0/0 CHAP: O CHALLENGE id 2 len 26 from "misco"
3d23h: Se0/0 CHAP: I CHALLENGE id 5 len 26 from "disco"
3d23h: Se0/0 CHAP: Using alternate hostname misco
3d23h: Se0/0 CHAP: O RESPONSE id 5 len 26 from "misco"
3d23h: Se0/0 CHAP: I RESPONSE id 2 len 26 from "disco"
3d23h: Se0/0 CHAP: O SUCCESS id 2 len 4
3d23h: Se0/0 CHAP: I SUCCESS id 5 len 4
3d23h: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0, changed state to
up

  • Ensure traffic from VLAN4, including any attached router interfaces to VLAN4, is hidden behind R5 Lo0 address when directed toward all external router networks.

The question requires NAT configuration from VLAN4 R5 FastEthernet0/0 to all external networks egressing from R5 ATM3/0. The configuration is not complex so this should start the alarm bells ringing again. Where else did you hear them? The DLSw+ was not difficult so it may be worth checking as this does not break any previous connectivity. In fact, you should get into the habit of frequently checking your work to ensure your points are still safe.

With NAT enabled, R5's VLAN4 interface will NAT from the original source address 10.50.50.1 into source address 10.5.5.5; this will affect the DLSw+ peering that has been configured. When DLSW+ initiates, two connections are set up between the routers; after a capabilities exchange, the router with the lowest peer IP address has its connection dropped with the other maintained. Originally R5 (10.50.50.1) had a higher peer IP address than R8 (10.8.8.8), so it dropped the connection to R8. Now R5 has been NAT'd into source address 10.5.5.5; however, R5 still uses the source address 10.50.50.1 for its peering and drops the connection to R8 believing it is lower than its own source address. R8, as it is promiscuous, sees a connection coming in from 10.5.5.5 and then drops the connection, which is lower than its own peer address of 10.8.8.8. You can imagine that the DLSW+ will never peer correctly now with both peers dropping their connections as shown in Example 1-59. The only way to overcome this is by excluding the actual DLSw+ process from the NAT. To do this you will have to know that DLSw+ over TCP uses ports 2065 and 2067 for read and write; these should, therefore, not be NAT'd. You could gain the port information from an appropriate debug but ideally you should know this. If you have configured this correctly as in Example 1-60, you have scored 3 points.

Example 1-59 R5 debug dlsw Output

R5#debug dlsw
4w0d: DLSw: START-TPFSM (peer 10.8.8.8(2065)): event:DLX-KEEPALIVE REQ
state:CONNECT
4w0d: DLSw: dtp_action_q() keepalive request from peer 10.8.8.8(2065)
4w0d: DLSw: Keepalive Response sent to peer 10.8.8.8(2065))
4w0d: DLSw: END-TPFSM (peer 10.8.8.8(2065)): state:CONNECT->CONNECT
4w0d: DLSw: dlsw_tcpd_fini() for peer 10.8.8.8(2065)
4w0d: DLSw: tcp fini closing connection for peer 10.8.8.8(2065)
4w0d: DLSw: START-TPFSM (peer 10.8.8.8(2065)): event:ADMIN-CLOSE CONNECTION state:CONNECT
4w0d: DLSw: dtp_action_b() close connection for peer 10.8.8.8(2065)
4w0d: DLSw: END-TPFSM (peer 10.8.8.8(2065)): state:CONNECT->DISCONN

Example 1-60 R5 Required NAT Modification Configuration

interface FastEthernet0/0
 ip address 10.50.50.1 255.255.255.248
 ip nat inside
 interface ATM3/0
 ip address 10.99.99.2 255.255.255.248
 ip nat outside
!
ip nat inside source list 100 interface Loopback0 overload
!
access-list 100 deny   tcp host 10.50.50.1 eq 2065 host 10.8.8.8
access-list 100 deny   tcp host 10.50.50.1 eq 2067 host 10.8.8.8
access-list 100 deny   tcp host 10.50.50.1 host 10.8.8.8 eq 2065
access-list 100 deny   tcp host 10.50.50.1 host 10.8.8.8 eq 2067
access-list 100 permit ip 10.50.50.0 0.0.0.255 any

  • A router is to be installed onto VLAN4 in the future. This router will have a default configuration, so allow R6 to assist dynamically to aid the configuration process. The router will require an IP address of 10.50.50.6 and should load a configuration file called R9-config from a fictitious TFTP server on 172.16.0.59.

The question requires that AutoInstall is used. This is a recent feature, which allows you to place a router with a default configuration onto a network, and it can be configured dynamically by receiving a DHCP address and TFTP server location for its own valid configuration. R6 is required to issue the DHCP address, TFTP server details, and default-router of R5 (10.50.50.1) that the router requires to contact the TFTP server on 172.16.0.59. The DHCP pool configuration on R6 excludes the majority of host addresses for network 10.50.50.0/29; this ensures that the only address offered to DHCP request is 10.50.50.6. You should notice that R6 is not connected to VLAN4 and AutoInstall works by DHCP request; for this reason, you must configure a helper-address on R5 to forward the request to R6. If you have configured this correctly as shown in Example 1-61 and Example 1-62, you have scored 5 points.

Example 1-61 R6 Required Configuration for AutoInstall

service dhcp
!
ip dhcp excluded-address 10.50.50.1 10.50.50.5
!
ip dhcp pool 1
   network 10.50.50.0 255.255.255.248
   bootfile R9-config
   option 150 ip 172.16.0.59
   default-router 10.50.50.1
!

Example 1-62 R5 VLAN4 DHCP Relay Configuration

interface FastEthernet0/0
 ip address 10.50.50.1 255.255.255.248
 ip helper-address 10.6.6.6

Pearson IT Certification Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from Pearson IT Certification 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 Pearson IT Certification 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@informit.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 Adobe 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.pearsonitcertification.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