Home > Articles > Cisco > CCNA Routing and Switching

CCNA SEC: Router Hardening

Hardening a router means that the router is secured against attacks as best as possible. This article discusses various means of making sure your routers are set up with maximum security, including manually hardening the router and router hardening with Cisco SDM.
Like this article? We recommend

We don’t tend to like people that are hardened. They can be cold and unsympathetic, and generally morose. We do, on the other hand, love it when our Cisco routers are hardened, especially when these routers live at the perimeter of our internal networks.

What exactly do we mean by router hardening? It means that the router is secured against attacks as best as possible. From secure, tough-to-crack passwords that are encrypted in the configurations, to the shutting down of unnecessary ports and services, the router has few vulnerabilities for would-be attackers to exploit.

For example, the router has built-in web server capabilities. That’s right. Your Cisco router can actually function as a web server on your network. Don’t plan on using the router as a web server? Be sure that this functionality is disabled.

In addition to web services, the Cisco router of today’s networks can provide many, many other potential services to the network. A key element to hardening the router is to find all of these services you are not using, and to disable them.

Manually Hardening the Router

Feel like going “old school” with your perimeter router security? Well, here is what you can do for configurations manually on the device in order to help secure (harden) it:

  • Disable unused router interfaces—that’s right, find ANY interface that is not in use and make sure you issue the shutdown command
  • Disable unused services—these typically include:
    • BOOTP
    • CDP
    • Configuration autoloading
    • FTP
    • TFTP
    • PAD
    • TCP and UDP minor services
    • DEC MOP
  • Disable management protocols that you are not using—these typically include:
    • SNMP
    • HTTP or HTTPS
    • DNS
  • Disable features that are techniques for re-directing your traffic:
    • ICMP Redirects
    • IP Source routing
  • Disable features that are techniques for probes and scans in reconnaissance attacks:
    • Finger
    • ICMP unreachables
    • ICMP mask reply
  • Ensure security of terminal connections:
    • IP identification service
    • TCP keepalives
  • Disable gratuitous ARP and proxy ARP
  • Disable IP-directed broadcasts

You also should inspect the network management protocols in use in your network infrastructure. Remember the following:

  • SNMP version 1 and 2c transfer passwords (called community strings) in clear text—if security is required—consider SNMP version 3.
  • HTTP authentication also sends clear text passwords—when needed, use HTTPS instead.
  • Attackers can respond to broadcast DNS lookups—disable DNS when not in use or configure securely.
  • Telnet is a clear text protocol—do not use it; instead, use SSH.

Router Hardening with the Cisco Router and Security and Device Manager (SDM)

Now one of the reasons that we love Cisco is that they are always trying to make it easy on us. We see this in the area of router hardening. In the Graphical User Interface for managing your perimeter routers, Cisco provides a Security Audit feature. This feature provides two “modes” of operation. The first is the Security Audit Wizard and the second is the One-step Lockdown mode.

The Security Audit Wizard examines your router and then lets you choose which potential security flaws you want to correct. The One-step Lockdown mode automatically makes the router hardening configurations that Cisco would recommend.

Here are the steps of the Security Audit Wizard:

  1. Within the Cisco SDM, choose Configure then Security Audit.
  2. Click the Perform Security Audit button.
  3. Click Next and the Security Audit Interface Configuration page appears —here you are presented with your router interfaces. It is up to you to select which of the interfaces connect to your internal networks, and which of the interfaces connect to your external networks. After you select these options, choose Next.
  4. The security audit now runs. When it is complete, the SDM presents you with a report of potential security vulnerabilities on your device. You can click Save Report in order to save it. If you select Close, the Security Audit Wizard continues to the next phase.
  5. In the final phase of the Security Audit Wizard, you can check or uncheck the vulnerabilities that you want the wizard to automatically repair. Notice there is even an option for Fix All.

As you might guess, using the One-step Lockdown mode is even easier!

  1. Within the Cisco SDM, choose Configure then Security Audit.
  2. Click the One-step Lockdown button.
  3. Click the Yes button that you want to continue and the SDM goes about its business of locking down the device for you.

What exactly does the One-step lockdown do on your device? Well, it is very busy indeed. Here is a list of the changes made by this GUI:

  • Disable Finger Service
  • Disable PAD Service
  • Disable TCP Small Servers Service
  • Disable UDP Small Servers Service
  • Disable IP BOOTP Server Service
  • Disable IP Identification Service
  • Disable CDP
  • Disable IP Source Route
  • Enable Password Encryption Service
  • Enable TCP Keepalives for Inbound Telnet Sessions
  • Enable TCP Keepalives for Outbound Telnet Sessions
  • Enable Sequence Numbers and Time Stamps on Debugs
  • Enable IP CEF
  • Disable IP Gratuitous ARPs
  • Set Minimum Password Length to Less Than 6 Characters
  • Set Authentication Failure Rate to Less Than 3 Retries
  • Set TCP Synwait Time
  • Set Banner
  • Enable Logging
  • Set Enable Secret Password
  • Disable SNMP
  • Set Scheduler Interval
  • Set Scheduler Allocate
  • Set Users
  • Enable Telnet Settings
  • Enable NetFlow Switching
  • Disable IP Redirects
  • Disable IP Proxy ARP
  • Disable IP Directed Broadcast
  • Disable MOP Service
  • Disable IP Unreachables
  • Disable IP Mask Reply
  • Disable IP Unreachables on NULL Interface
  • Enable Unicast RPF on Outside Interfaces
  • Enable Firewall on All of the Outside Interfaces
  • Set Access Class on HTTP Server Service
  • Set Access Class on VTY Lines
  • Enable SSH for Access to the Router

Router Hardening with the Cisco’s AutoSecure

Cisco also provides a One-step lockdown-like feature at the command line! This feature is called AutoSecure. It uses the command shown below:

auto secure [management | forwarding] [no-interact | full]
 [ntp | login | ssh | firewall | tcp-intercept]

Notice that this command can run fully automated like the One-step Lockdown mode of the Security Audit feature in SDM. You would issue the command auto secure no-interact. You should notice also that you can run “subsets” of the command’s full capabilities. For example, you could run auto secure management in order to just harden the network management capabilities of the router.

You might not be surprised to learn that the Command Line AutoSecure feature is capable of doing a bit more than the graphical user interface counterpart. Specifically, Cisco SDM does not implement these Cisco AutoSecure features:

  • Disabling NTP
  • Configuring AAA
  • Setting SPD values
  • Enabling TCP intercepts
  • Configuring antispoofing ACLs on outside interfaces

The Cisco SDM also implements some of the Cisco AutoSecure features differently. For example:

  • The SDM disables SNMP but does not configure SNMPv3 (on some routers).
  • The SDM enables and configures SSH on crypto Cisco IOS images, but does not enable SCP or disable other access and file transfer services, such as FTP for example.

Conclusion

As we have seen, there is more than one option when it comes to ensuring that your Cisco router is well protected against security vulnerabilities. Essentially, two GUI options exist within the Cisco SDM, and a very powerful command line option exists. Of course, administrators can always walk through configuration manually. Whatever you choose, progress with a plan of carefully testing to ensure your router hardening configurations do not cause disruptions within your production network. It is wonderful to be secure, but you do not want this security at the risk of a lack of functionality. We love the help desk phones to remain quiet!

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