Home > Articles > Software Development & Management

Like this article? We recommend

Like this article? We recommend

Migrating to the Solaris Operating System: The Discipline of UNIX-to-UNIX MigrationsMigrating to the Solaris Operating System: The Discipline of UNIX-to-UNIX Migrations

Learn More Buy

Like this article? We recommend

Like this article? We recommend

Migrating to the Solaris Operating System: The Discipline of UNIX-to-UNIX MigrationsMigrating to the Solaris Operating System: The Discipline of UNIX-to-UNIX Migrations

Learn More Buy

Layer 3—OSPF Network Redundancy— Rapid Convergence

Open shortest path first (OSPF) is an intradomain, link-state routing protocol. The main idea of OSPF is that each OSPF router is able to determine the state of the link to all neighbor routers and the associated costs. One property of this routing protocol is that each OSPF router has a view of the entire network, which allows it to find the best path to all participating routers.

All OSPF routers in the domain flood each other with link state packets (LSP), which contain the unique ID of the sending router; a list of directly connected neighbor routers and associated costs; a sequence number and a time to live, authentication, hierarchy, load balancing, and checksum information. From this information, each node can reliably determine if this LSP is the most recent by comparing seq number and computing the shortest path to every node, then collecting all LSPs from all nodes and comparing costs, using Dijstras' shortest path algorithm. To prevent continuous flooding, the sender never receives the same LSP packet that he sent out.

To better understand OSPF for suitability from an availability perspective, the following lab network was set up, consisting of Extreme Network switches and Sun servers. FIGURE 15 describes the actual setup used to demonstrate availability characteristics of the interior routing protocol OSPF.

Figure 15FIGURE 15 Design Pattern—OSPF Network

To confirm correct configuration, traceroutes were performed from client to server. In the following output, the highlighted lines show the path through sw2:

client># traceroute server
traceroute: Warning: Multiple interfaces found; using 16.0.0.51 @ hme0
traceroute to server (11.0.0.51), 30 hops max, 40 byte packets
 1 16.0.0.1 (16.0.0.1) 1.168 ms 0.661 ms 0.523 ms
 2 15.0.0.1 (15.0.0.1) 1.619 ms 1.104 ms 1.041 ms
 3 17.0.0.1 (17.0.0.1) 1.527 ms 1.197 ms 1.043 ms
 4 18.0.0.1 (18.0.0.1) 1.444 ms 1.208 ms 1.106 ms
 5 12.0.0.1 (12.0.0.1) 1.237 ms 1.274 ms 1.083 ms
 6 server (11.0.0.51) 0.390 ms 0.349 ms 0.340 ms

The following tables show the initial routing tables of the core routers. The first two highlighted lines in CODE EXAMPLE 2 show the route to the client through sw2. The second two highlighted lines show the sw2 path.

CODE EXAMPLE 2 Router sw1 Routing Table 

 OR Destination    Gateway     Mtr  Flags   Use M-Use VLAN   Acct-1
*s 10.100.0.0/24   12.0.0.1     1 UG---S-um  63   0 net12  0   
*oa 11.0.0.0/8     12.0.0.1     5 UG-----um  98   0 net12  0   
*d 12.0.0.0/8     12.0.0.2     1 U------u- 1057   0 net12  0   
*d 13.0.0.0/8     13.0.0.1     1 U------u-  40   0 net13  0   
*oa 14.0.0.0/8     13.0.0.2     8 UG-----um   4   0 net13  0   
*oa 15.0.0.0/8     18.0.0.2     12 UG-----um   0   0 net18  0   
*oa 15.0.0.0/8     13.0.0.2     12 UG-----um   0   0 net13  0   
*oa 16.0.0.0/8     18.0.0.2     13 UG-----um   0   0 net18  0   
*oa 16.0.0.0/8     13.0.0.2     13 UG-----um   0   0 net13  0   
*oa 17.0.0.0/8     18.0.0.2     8 UG-----um   0   0 net18  0   
*d 18.0.0.0/8     18.0.0.1     1 U------u-  495   0 net18  0   
*d 127.0.0.1/8    127.0.0.1     0 U-H----um   0   0 Default 0   

Origin(OR): b - BlackHole, bg - BGP, be - EBGP, bi - IBGP, bo - BOOTP, ct - CBT
      d - Direct, df - DownIF, dv - DVMRP, h - Hardcoded, i - ICMP
      mo - MOSPF, o - OSPF, oa - OSPFIntra, or - OSPFInter, oe - OSPFAsExt
      o1 - OSPFExt1, o2 - OSPFExt2, pd - PIM-DM, ps - PIM-SM, r - RIP
      ra - RtAdvrt, s - Static, sv - SLB_VIP, un - UnKnown.

Flags: U - Up, G - Gateway, H - Host Route, D - Dynamic, R - Modified,
    S - Static, B - BlackHole, u - Unicast, m - Multicast.

Total number of routes = 12.

Mask distribution:
  11 routes at length 8      1 routes at length 24

CODE EXAMPLE 3 Router sw2 Routing Table 

sw2:8 # sh ipr

 OR Destination    Gateway     Mtr  Flags   Use M-Use VLAN   Acct-1
*s 10.100.0.0/24   18.0.0.1     1 UG---S-um  27   0 net18  0   
*oa 11.0.0.0/8     18.0.0.1     9 UG-----um  98   0 net18  0   
*oa 12.0.0.0/8     18.0.0.1     8 UG-----um   0   0 net18  0   
*oa 13.0.0.0/8     18.0.0.1     8 UG-----um   0   0 net18  0   
*oa 14.0.0.0/8     17.0.0.2     8 UG-----um   0   0 net17  0   
*oa 15.0.0.0/8     17.0.0.2     8 UG-----um   9   0 net17  0   
*oa 16.0.0.0/8     17.0.0.2     9 UG-----um   0   0 net17  0   
*d 17.0.0.0/8     17.0.0.1     1 U------u-  10   0 net17  0   
*d 18.0.0.0/8     18.0.0.2     1 U------u-  403   0 net18  0   
*d 127.0.0.1/8    127.0.0.1     0 U-H----um   0   0 Default 0   
#
#

CODE EXAMPLE 4 Router sw3 Routing Table

sw3:5 # sh ipr

 OR Destination    Gateway     Mtr  Flags   Use M-Use VLAN   Acct-1
*s 10.100.0.0/24   13.0.0.1     1 UG---S-um  26   0 net13  0   
*oa 11.0.0.0/8     13.0.0.1     9 UG-----um   0   0 net13  0   
*oa 12.0.0.0/8     13.0.0.1     8 UG-----um  121   0 net13  0   
*d 13.0.0.0/8     13.0.0.2     1 U------u-  28   0 net13  0   
*d 14.0.0.0/8     14.0.0.1     1 U------u-  20   0 net14  0   
*oa 15.0.0.0/8     14.0.0.2     8 UG-----um   0   0 net14  0   
*oa 16.0.0.0/8     14.0.0.2     9 UG-----um   0   0 net14  0   
*oa 17.0.0.0/8     14.0.0.2     8 UG-----um   0   0 net14  0   
*oa 18.0.0.0/8     13.0.0.1     8 UG-----um   0   0 net13  0   
*d 127.0.0.1/8    127.0.0.1     0 U-H----um   0   0 Default 0

The first two highlighted lines in CODE EXAMPLE 5 show the route back to the server through sw4, using the first in the table. The second two highlighted lines show the sw2 path.

CODE EXAMPLE 5 Switch sw4 Routing Table

sw4:8 # sh ipr

 OR Destination    Gateway     Mtr  Flags   Use M-Use VLAN   Acct-1
*s 10.100.0.0/24   14.0.0.1     1 UG---S-um  29   0 net14  0   
*oa 11.0.0.0/8     17.0.0.1     13 UG-----um   0   0 net17  0   
*oa 11.0.0.0/8     14.0.0.1     13 UG-----um   0   0 net14  0   
*oa 12.0.0.0/8     17.0.0.1     12 UG-----um   0   0 net17  0   
*oa 12.0.0.0/8     14.0.0.1     12 UG-----um   0   0 net14  0   
*oa 13.0.0.0/8     14.0.0.1     8 UG-----um   0   0 net14  0   
*d 14.0.0.0/8     14.0.0.2     1 U------u-  12   0 net14  0   
*d 15.0.0.0/8     15.0.0.1     1 U------u-  204   0 net15  0   
*oa 16.0.0.0/8     15.0.0.2     5 UG-----um   0   0 net15  0   
*d 17.0.0.0/8     17.0.0.2     1 U------u-  11   0 net17  0   
*oa 18.0.0.0/8     17.0.0.1     8 UG-----um   0   0 net17  0   
*d 127.0.0.1/8    127.0.0.1     0 U-H----um   0   0 Default 0

To check failover capabilities on the OSPF, the interface on the switch sw2 was damaged to create a failure and a constant ping was run from the client to the server.

The interface on the switch sw2 was removed, and the measurement of failover was performed as shown in the following output. The first highlighted line shows when the interface sw2 fails. The second highlighted line shows that the new switch interface sw3 route is established in two seconds.

client reading:

64 bytes from server (11.0.0.51): icmp_seq=11. time=2. ms
64 bytes from server (11.0.0.51): icmp_seq=12. time=2. ms
ICMP Net Unreachable from gateway 17.0.0.1
 for icmp from client (16.0.0.51) to server (11.0.0.51)
ICMP Net Unreachable from gateway 17.0.0.1
 for icmp from client (16.0.0.51) to server (11.0.0.51)
64 bytes from server (11.0.0.51): icmp_seq=15. time=2. ms
64 bytes from server (11.

OSPF took approximately two seconds to detect and recover from the failed node.

The highlighted lines in following output from the traceroute server command show the new path from the client to the server through the switch interface sw3.

client># traceroute server
traceroute: Warning: Multiple interfaces found; using 16.0.0.51 @ hme0
traceroute to server (11.0.0.51), 30 hops max, 40 byte packets
 1 16.0.0.1 (16.0.0.1) 0.699 ms 0.535 ms 0.581 ms
 2 15.0.0.1 (15.0.0.1) 1.481 ms 0.990 ms 0.986 ms
 3 14.0.0.1 (14.0.0.1) 1.214 ms 1.021 ms 1.002 ms
 4 13.0.0.1 (13.0.0.1) 1.322 ms 1.088 ms 1.100 ms
 5 12.0.0.1 (12.0.0.1) 1.245 ms 1.131 ms 1.220 ms
 6 server (11.0.0.51) 1.631 ms 1.200 ms 1.314 ms

The following code examples show the routing tables after the node failure. The first highlighted line in CODE EXAMPLE 6 shows the new route to the server through the switch sw3. The second highlighted line shows that the swithch sw2 link is down.

CODE EXAMPLE 6 Switch sw1 Routing Table After Node Failure

sw1:27 # sh ipr

 OR Destination    Gateway     Mtr  Flags   Use M-Use VLAN   Acct-1
*s 10.100.0.0/24   12.0.0.1     1 UG---S-um  63   0 net12  0   
*oa 11.0.0.0/8     12.0.0.1     5 UG-----um  168   0 net12  0   
*d 12.0.0.0/8     12.0.0.2     1 U------u- 1083   0 net12  0   
*d 13.0.0.0/8     13.0.0.1     1 U------u-  41   0 net13  0   
*oa 14.0.0.0/8     13.0.0.2     8 UG-----um   4   0 net13  0   
*oa 15.0.0.0/8     13.0.0.2     12 UG-----um   0   0 net13  0   
*oa 16.0.0.0/8     13.0.0.2     13 UG-----um  22   0 net13  0   
*oa 17.0.0.0/8     13.0.0.2     12 UG-----um   0   0 net13  0   
 d 18.0.0.0/8     18.0.0.1     1 ---------  515   0 -------- 0   
*d 127.0.0.1/8    127.0.0.1     0 U-H----um   0   0 Default 0

CODE EXAMPLE 7 Switch sw2 Routing Table After Node Failure 

sw1:4 # sh ipr

 OR Destination    Gateway     Mtr  Flags   Use M-Use VLAN   Acct-1
*s 10.100.0.0/24   12.0.0.1     1 UG---S-um  63   0 net12  0   
*oa 11.0.0.0/8     12.0.0.1     5 UG-----um  168   0 net12  0   
*d 12.0.0.0/8     12.0.0.2     1 U------u- 1102   0 net12  0   
*d 13.0.0.0/8     13.0.0.1     1 U------u-  41   0 net13  0   
*oa 14.0.0.0/8     13.0.0.2     8 UG-----um   4   0 net13  0   
*oa 15.0.0.0/8     13.0.0.2     12 UG-----um   0   0 net13  0   
*oa 16.0.0.0/8     13.0.0.2     13 UG-----um  22   0 net13  0   
*oa 17.0.0.0/8     13.0.0.2     12 UG-----um   0   0 net13  0   
 d 18.0.0.0/8     18.0.0.1     1 ---------  515   0 -------- 0   
*d 127.0.0.1/8    127.0.0.1     0 U-H----um   0   0 Default 0

CODE EXAMPLE 8 Switch sw3 Routing Table After Node Failure

sw3:6 # sh ipr

 OR Destination    Gateway     Mtr  Flags   Use M-Use VLAN   Acct-1
*s 10.100.0.0/24   13.0.0.1     1 UG---S-um  26   0 net13  0   
*oa 11.0.0.0/8     13.0.0.1     9 UG-----um  24   0 net13  0   
*oa 12.0.0.0/8     13.0.0.1     8 UG-----um  134   0 net13  0   
*d 13.0.0.0/8     13.0.0.2     1 U------u-  29   0 net13  0   
*d 14.0.0.0/8     14.0.0.1     1 U------u-  20   0 net14  0   
*oa 15.0.0.0/8     14.0.0.2     8 UG-----um   0   0 net14  0   
*oa 16.0.0.0/8     14.0.0.2     9 UG-----um  25   0 net14  0   
*oa 17.0.0.0/8     14.0.0.2     8 UG-----um   0   0 net14  0   
*d 127.0.0.1/8    127.0.0.1     0 U-H----um   0   0 Default 0

The highlighted line in CODE EXAMPLE 9 shows the new route back to the client through sw3.

CODE EXAMPLE 9 Switch sw4 Routing Table After Node Failure

sw4:9 # sh ipr

 OR Destination    Gateway     Mtr  Flags   Use M-Use VLAN   Acct-1
*s 10.100.0.0/24   14.0.0.1     1 UG---S-um  29   0 net14  0   
*oa 11.0.0.0/8     14.0.0.1     13 UG-----um  21   0 net14  0   
*oa 12.0.0.0/8     14.0.0.1     12 UG-----um   0   0 net14  0   
*oa 13.0.0.0/8     14.0.0.1     8 UG-----um   0   0 net14  0   
*d 14.0.0.0/8     14.0.0.2     1 U------u-  12   0 net14  0   
*d 15.0.0.0/8     15.0.0.1     1 U------u-  216   0 net15  0   
*oa 16.0.0.0/8     15.0.0.2     5 UG-----um  70   0 net15  0   
*d 17.0.0.0/8     17.0.0.2     1 U------u-  12   0 net17  0   
*d 127.0.0.1/8    127.0.0.1     0 U-H----um   0   0 Default 0

OSPF is a good routing protocol with enterprise networks. It has fast failure detection and recovery. However, there are security concerns that should be investigated prior to deployment.

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.

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