Home > Articles > Networking

Cisco ISP Software and Router Management

Jun 7, 2002

📄 Contents

␡

⎙ Print

< Back Page 7 of 8 Next >

This chapter is from the book 

Cisco ISP Essentials

Learn More Buy

DNS and Routers

The DNS might be an unusual topic to put into a book covering ISP network essentials and Cisco IOS Software best practices. However, it is one of the most overlooked systems topics in the ISP industry—yet it is probably the most important part of the public visibility of the network to get right. If the DNS does not work, the public thinks that the network is broken—many newspaper headlines in the last few years have displayed such apocryphal headlines simply because of operational errors or problems with the DNS.

An ISP network engineer must pay attention to two aspects of the DNS. The first is the business of putting all the name-to-address-to-name mappings in the system so that routers can be recognized by their English-language names rather than by four boring decimal numbers separated by dots. Humans aren't good at remembering the latter. The second aspect is to actually enable support for the DNS in the routers themselves. This section covers only the router aspect—Chapter 5, "Operational Practices," describes configuration and placement of the DNS systems throughout the ISP backbone.

Mapping IP Addresses to Names

Mapping domain names to IP addresses and vice versa is one of those commonly overlooked areas in a new ISP's operations. Doing a trace from Australia across the backbones in the United States to a site in the United Kingdom gives you something like Example 2-3.

Example 2-2 Example Traceroute Across the Internet from Australia to the United Kingdom

traceroute to k.root-servers.net (193.0.14.129), 30 hops max, 38 byte packets
 1 fe5-0.gw.apnic.net (202.12.29.190) 0.707 ms 0.534 ms 0.497 ms
 2 Serial1-0-3.cha8.Brisbane.telstra.net (139.130.64.97) 5.999 ms 5.131 ms 
  6.155 ms
 3 GigabitEthernet5-1.cha-core4.Brisbane.telstra.net (203.50.51.1) 6.148 ms
  4.972 ms 4.537 ms
 4 Pos2-0.chw-core2.Sydney.telstra.net (203.50.6.225) 19.355 ms 18.595 ms
  19.797 ms
 5 Pos4-0.exi-core1.Melbourne.telstra.net (203.50.6.18) 32.120 ms 32.968 ms 
  32.544 ms
 6 Pos5-0.way-core4.Adelaide.telstra.net (203.50.6.162) 50.088 ms 46.171 ms 
  44.896 ms
 7 Pos6-0.wel-core3.Perth.telstra.net (203.50.6.194) 88.296 ms 75.545 ms 
  83.527 ms
 8 GigabitEthernet4-0.wel-gw1.Perth.telstra.net (203.50.113.18) 78.172 ms
  76.116 ms 75.851 ms
 9 Pos1-0.paix1.PaloAlto.net.reach.com (203.50.126.30) 305.915 ms 309.617 ms
   314.994 ms
10 fe0.pao0.verio.net (198.32.176.47) 308.744 ms 304.431 ms 304.230 ms
11 p4-6-0-0.r02.mclnva02.us.bb.verio.net (129.250.2.246) 380.061 ms 380.639 ms 
  380.292 ms
12 p16-0-0-0.r01.mclnva02.us.bb.verio.net (129.250.5.253) 384.100 ms 384.124 ms 384.382 ms
13 p4-7-2-0.r00.nycmny06.us.bb.verio.net (129.250.3.181) 390.487 ms 390.300 ms 
  396.328 ms
14 p4-0-2-0.r01.nycmny06.us.bb.verio.net (129.250.3.130) 390.196 ms 384.921 ms 
  385.245 ms
15 gxn.d3-1-0-1.r01.nycmny06.us.bb.verio.net (129.250.16.198) 321.844 ms
  319.204 ms 319.252 ms
16 se6-1-0-llb-x-ny2.NY1.core.rtr.xara.net (194.143.164.45) 325.706 ms 320.925 ms
  320.557 ms
17 se5-1-llb-ny1.HU1.core.rtr.xara.net (194.143.164.97) 325.264 ms 322.578 ms
  321.049 ms
18 po2-0-llb-hu1.TH30.core.rtr.xara.net (194.143.164.189) 389.618 ms 390.177 ms
  388.401 ms
19 gb11-0-0-llb-x-many.TH1.core.rtr.uk.xo.net (194.143.163.130) 398.421 ms 
  388.459 ms 390.471 ms
20 fa0-0.gxn-linx.transit1.linx.net (195.66.248.33) 388.834 ms 391.937 ms
  389.687 ms
21 k.root-servers.net (193.0.14.129) 387.544 ms 391.093 ms 387.059 ms

Notice that each router IP address has a corresponding DNS entry. These very descriptive DNS names help Internet users and operators understand what is happening with their connections and which route the outbound traffic is taking. The descriptive names are an invaluable aid to troubleshooting problems on the net.

Table 2-2 shows some examples of descriptive DNS formats used by various ISPs.

Table 2-2 DNS Formats

ISP	Example Use of the DNS
C&W	bordercore4-hssi0-0.SanFrancisco.cw.net
BBN Planet	p2-0.paloalto-nbr2.bbnplanet.net
Concert	core1-h1-0-0.uk1.concert.net
Sprint	sl-bb6-dc-1-1-0-T3.sprintlink.net
DIGEX	sjc4-core5-pos4-1.atlas.digex.net
Verio	p0-0-0.cr1.mtvwca.pacific.verio.net
IIJ	otemachi5.iij.net
Qwest	sfo-core-03.inet.qwest.net
Telstra BigPond	Pos5-0-0.cha-core2.Brisbane.telstra.net
UUNET	ATM2-0.BR1.NYC5.ALTER.NET
Teleglobe	if-8-0.core1.NewYork.Teleglobe.net
VSNL	E3-VSB1-LVSB.Bbone.vsnl.net.in
KDD Internet	gsr-ote3.kddnet.ad.jp
ChinaNet	p-10-1-0-r1-s-bjbj-1.cn.net

DNS Resolver in IOS Software

You can specify a default domain name that the Cisco IOS Software will use to complete domain name requests for functions such as Telnet, TFTP, and other instances of name completion (for example, ip ospf domain-lookup). You can specify either a single domain name or a list of domain names. Any IP host name that does not contain a domain name will have the domain name that you specify appended to it before being added to the host table.

ip domain-name name
ip domain-list name

It is also advisable to include a name server for the router to resolve the DNS request:

ip name-server server-address1 [[server-address2]...server-address6]

Remember that the current practice on the Internet is to quote at least two DNS resolvers. The reason is the same as for any other situation: redundancy. If one DNS server disappears, the other one can take over. When both are there, the router will look up the servers in a round-robin fashion for each request.

< Back Page 7 of 8 Next >

🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

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

Privacy Notice

Overview

Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about 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 InformIT. 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.informit.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

Email Address