Home > Articles > Cisco > CCNP Security

Securing Cisco Routers

  • Print
  • + Share This
This chapter is from the book

Securing Routers by Disabling Unused Router Services and Interfaces

On Cisco routers, a whole bunch of services come enabled by default. As a network security expert, your first order of operation would be to ensure that the unused services are disabled.

We now give you a rundown of a few services that you need know before entering into the security arena.

bootp

bootp is enabled by default, and if you are not using it, you should definitely disable it. You can use the no ip bootp server command in global configuration mode to disable bootp on your routers:

Central(config)# no ip bootp server

CDP

Cisco Discovery Protocol (CDP) is also enabled by default, and we highly recommend that you disable this service on the router globally. You can disable CDP globally by using the no cdp run command in global configuration mode, or you can disable CDP on a per-interface basis by using the no cdp enable command in interface configuration mode:

Central(config)#no cdp run
Central(config-if)#no cdp enable

CAUTION

The no cdp run command disables CDP globally on the routers.

ip classless

The ip classless command is enabled on the Cisco routers by default in version 12.0 and higher. Disable ip classless if your network does not have a subnetted range of IP addresses. If you are subnetting a block of IP address allocated to you by the American Registry for Internet Numbers (ARIN), you should ensure that ip classless is enabled. You can learn more about ARIN by going to http://www.arin.net. It allows the router to advertise the subnetted addresses to its neighbors:

Central(config)#no ip classless

DNS

Domain Name System (DNS) lookup is enabled by default on Cisco routers, and if you are not implementing DNS lookup on your network, it is highly advisable to disable this feature globally by using the no ip domain-lookup command:

Central(config)#no ip domain-lookup

finger

The finger command is enabled by default and can be used to see what users are logged on to the network device. The finger command has been documented in RFC 742, and you should globally disable the finger command on network devices:

Central(config)#no ip finger

CAUTION

The no service finger command has been replaced by the no ip finger command.

CAUTION

Finger service can be disabled on the router in global configuration mode.

HTTP

Cisco routers can be accessed via a Web page, and unless you are implementing authentication proxy, we highly recommend that you turn off the HTTP service running on the router. You can use the no ip http server command to disable it.

If you want to implement HTTP-based management, we recommend that you implement HTTP authentication and limit the HTTP connections to the router using ACLs.

ip mask-reply

By default, the ip mask-reply command is disabled on all Cisco routers. The mask replies respond to Internet Control Message Protocol (ICMP) mask requests by sending out ICMP mask replies, and these mask replies contain important network information. If mask replies are enabled, make sure you disable them on the router by using the no ip mask-reply command in interface configuration mode:

Central(config-if)#no ip mask-reply

IP-Directed Broadcast

The IP-directed broadcast is another service that is commonly used in Smurf attacks. Smurf attacks send ICMP echo requests from a spoofed source address to a directed broadcast that cause all hosts to respond to the ping echo request, creating a lot of traffic on the network. By default on IOS version 12.0 and higher, ip directed broadcast is disabled, and if you are running any version lower than 12.0, it is imperative that you disable IP directed broadcasts on the router by issuing the following command in interface configuration mode:

Central(config-if)#no ip directed-broadcast

CAUTION

Smurf attacks send ICMP echo requests from a spoofed source address to a directed broadcast that cause all hosts to respond to the ping echo request, creating a lot of traffic on the network.

IP Source Routing

IP source routing allows the sender of an IP packet to control the route that packet will take to reach the destination endpoint. By default, IP source routing is disabled on the routers and should only be enabled if your network needs call for it. The following command disables IP source routing on the router globally:

Central(config)#no ip source-route

CAUTION

IP source routing allows the sender of an IP packet to control the route that packet will take to reach the destination endpoint.

IP Unreachable

IP unreachable messages can be used to map out the network topology, and they should be disabled on all interfaces. You can disable IP unreachables on all interfaces by issuing the following command in interface configuration mode:

Central(config-if)#no ip unreachables

CAUTION

IP unreachables should be disabled on all interfaces connected to insecure networks.

Small Servers

Cisco classifies echo, chargen, daytime, and discard as small services and recommends that these services be disabled on the router. By default, on versions 11.3 or higher, the small server service is disabled by default.

  • + Share This
  • 🔖 Save To Your Account

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