Cisco CCNA Certification Exam Tutorial: Frame Relay DLCIs And Mappings

Writen by Chris Bryant

Passing the CCNA is tough, and one of the toughest parts is keeping all the acronyms straight! Frame Relay has plenty of those, and today we’re going to examine what DLCIs do and how they’re mapped on a Cisco router.

Frame Relay VCs use Data-Link Connection Identifiers (DLCI – pronounced “del-see”) as their addresses. Unlike other Cisco technologies, VCs have only a single DLCI in their header. They do not have a source and destination.

DLCIs have local significance only. DLCI numbers are not advertised to other routers, and other routers can use the same DLCI numbers without causing connectivity issues.

Cisco uses the term global addressing to describe a technique by which a router in a frame relay network is reached via the same DLCI number from each router in the network. For example, in a 25-router network, the same DLCI number would be used to reach “Router A” by each router.

Global Addressing is an organizational tool that does not affect the fact that DLCIs have local significance only.

The locally significant DLCI must be mapped to the destination router’s IP address. There are two options for this, Inverse ARP and static mapping.

In both of the following examples, the single physical Serial interface on Router 1 is configured with two logical connections through the frame relay cloud, one to Router 2 and one to Router 3.

Inverse ARP runs by default once Frame Relay is enabled, and starts working as soon as you open the interface. By running show frame-relay map after enabling Frame Relay, two dynamic mappings are shown on this router. If a dynamic mapping is shown, Inverse ARP performed it.

R1#show frame map

Serial0 (up): ip 200.1.1.2 dlci 122(0×7A,0×1CA0), dynamic,

broadcast,, status defined, active

Serial0 (up): ip 200.1.1.3 dlci 123(0×7B,0×1CB0), dynamic,

broadcast,, status defined, active

Static mappings require the use of a frame map statement. To use static mappings, turn Inverse ARP off with the no frame-relay inverse-arp statement, and configure a frame map statement for each remote destination that maps the local DLCI to the remote IP address. Frame Relay requires the broadcast keyword to send broadcasts to the remote device.

R1#conf t

R1(config)#interface serial0

R1(config-if)#no frame-relay inverse-arp

R1(config-if)#frame map ip 200.1.1.2 122 broadcast

R1(config-if)#frame map ip 200.1.1.3 123 broadcast

The syntax of the frame map statement maps the remote IP address to the local DLCI. Broadcasts will not be transmitted by default; the broadcast option must be configured.

R1#show frame map

Serial0 (up): ip 200.1.1.2 dlci 122(0×7A,0×1CA0), static,

broadcast,

CISCO, status defined, active

Serial0 (up): ip 200.1.1.3 dlci 123(0×7B,0×1CB0), static,

broadcast,

CISCO, status defined, active

Hands-on practice is the best way to prepare for CCNA exam success. Working with Frame Relay in a lab environment practically guarantees that you’ll truly master the concepts shown here – and then you’re on your way to the CCNA and becoming a master network engineer.

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage, home of free CCNA and CCNP tutorials, The Ultimate CCNA Study Package, and Ultimate CCNP Study Packages.

You can also join his RSS feed and visit his blog, which is updated several times daily with new Cisco certification articles, free tutorials, and daily CCNA / CCNP exam questions! Details are on the website.

For a FREE copy of his latest e-books, “How To Pass The CCNA” and “How To Pass The CCNP”, visit the website and download your free copies. You can also get FREE CCNA and CCNP exam questions every day! Get your CCNA study guide from The Bryant Advantage!

Cisco Certification: A Survival Guide To The Cisco Cable Jungle

Writen by Chris Bryant

One of the most confusing parts of beginning your Cisco studies is keeping all the cable types separate in your mind, and then remembering what they’re used for. This often occurs when a CCNA or CCNP candidate starts putting together their own home practice lab, and they suddenly realize that they have the equipment to run labs, but not the cables.

With this in mind, here are some common Cisco cable types and their primary use.

First, there’s the regular old “straight-through cable”, so named because the eight wires inside the cable go straight through the wire. While the wires may be twisted inside to reduce electromagnetic interference (EMI), the wire that’s connected to Pin 1 on one end is connected to Pin 1 on the other end, and so on. In a home lab, a straight-through cable is often used to connect a switch port to an Ethernet port on a router, with a transceiver attached to the Ethernet port. Straight-through cables are also good for connecting a BRI interface to an ISDN simulator.

The “crossover cable” is so named because the wires do cross over between pins. This allows the devices to both send and receive at the same time, and crossover cables are a must for directly connecting ports on Cisco switches to create a trunk.

The “rollover cable” allows you to connect directly to a Cisco console port with your laptop or PC. This is the blue cable that comes with new Cisco devices, and it’s the one that engineers tend to hold on to with their lives. Without a rollover cable (also commonly called a “console cable”), you can’t connect your laptop directly to a Cisco device.

Finally, there’s the DTE/DCE cable. To create a frame relay cloud in your home lab (using one of your Cisco routers as a DCE), or to directly connect two Cisco routers via their serial interfaces, you will need a DTE/DCE cable. Remember that the DCE interface will need to supply clockrate to the DTE interface.

The different cable types can be confusing when you first read about them, but after tearing down or building your home lab a few times, you’ll definitely have them straight come test day!

Best of luck in your lab and your exams.

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage, home of free CCNA and CCNP tutorials, The Ultimate CCNA Study Package, and Ultimate CCNP Study Packages. For a FREE copy of his latest e-books, “How To Pass The CCNA” and “How To Pass The CCNP”, visit the website and download your free copies. You can also get FREE CCNA and CCNP exam questions every day! Pass the CCNA exam with The Bryant Advantage!

Cisco CCNP Certification / BCMSN Exam Tutorial: Writing QoS Policy

Writen by Chris Bryant

QoS – Quality of Service – is a huge topic on both the BCMSN exam and real-world networks. QoS is so big today that Cisco’s created separate specialist certifications that cover nothing but QoS! It can be an overwhelming topic at first, but master the fundamentals and you’re on your way to exam and job success.

If you work with QoS at any level – and sooner or later, you will – you’ve got to know how to write and apply QoS policies.

Creating and applying such a policy is a three-step process.

1. Create a QoS class to identify the traffic that will be affected by the policy.

2. Create a QoS policy containing the actions to be taken by traffic identified by the class.

3. Apply the policy to the appropriate interfaces.

If the phrase “identify the traffic” sounds like it’s time to write an access-list, you’re right! Writing an ACL is one of two ways to classify traffic, and is the more common of the two. Before we get to the less-common method, let’s take a look at how to use an ACL to classify traffic.

You can use either a standard or extended ACL with QoS policies. The ACL will be written separately, and then called from the class map.

SW1(config)#access-list 105 permit tcp any any eq 80

SW1(config)#class-map WEBTRAFFIC

SW1(config-cmap)#match access-group 105

Now that we’ve identified the traffic to be affected by the policy, we better get around to writing the policy! QoS policies are configured with the policy-map command, and each clause of the policy will contain an action to be taken to traffic matching that clause.

SW1(config)#policy-map LIMIT_WEBTRAFFIC_BANDWIDTH

SW1(config-pmap)#class WEBTRAFFIC

SW1(config-pmap-c)#police 5000000 exceed-action drop

SW1(config-pmap-c)#exit

This is a simple policy, but it illustrates the logic of QoS policies. The policy map LIMIT_WEBTRAFFIC_BANDWIDTH calls the map-class WEBTRAFFIC. We already know that all WWW traffic will match that map class, so any WWW traffic that exceeds the stated bandwidth limitation will be dropped.

Finally, apply the policy to the appropriate interface.

SW1(config-if)#service-policy LIMIT_WEBTRAFFIC_BANDWIDTH in

Getting your CCNP is a great way to boost your career, and learning QoS is a tremendous addition to your skill set. Like I said, learn the fundamentals, don’t get overwhelmed by looking at QoS as a whole, and you’re on your way to success!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage, home of free CCNP and CCNA tutorials, The Ultimate CCNA Study Package, and Ultimate CCNP Study Packages.

You can also join his RSS feed and visit his blog, which is updated several times daily with new Cisco certification articles, free tutorials, and daily CCNA / CCNP exam questions! Details are on the website.

For a FREE copy of his latest e-books, “How To Pass The CCNA” and “How To Pass The CCNP”, just visit the website! You can also get FREE CCNA and CCNP exam questions every day! Get your CCNP certification with The Bryant Advantage!

Cisco CCNA Certification Exam Tutorial: Variance And Unequal Cost Load Balancing

Writen by Chris Bryant

To pass the CCNA exam, you’ve got to know how to work with IGRP and EIGRP unequal-cost load balancing. You may not see much IGRP in production networks anymore, but you’ll see a lot of EIGRP, and part of fine-tuning your EIGRP network is making sure that all paths are in use while allowing for varying bandwidth rates.

Using the variance command is the easy part – it’s getting the metric that’s the hard part with IGRP. With EIGRP, you just look in the topology table and that’s it. With IGRP, you’ve got to run a debug to get the right metric.

The variance command is a multiplier when the value supplied with the variance command is multiplied by the lowest-cost metric, it must exceed the higher-cost metric in order for the higher-cost route to be added.

If that sounds complicated, it’s not. It’s one of those things that sounds difficult, but isn’t. Trust me!

In this example, R1 has two paths to 172.23.0.0, but is currently using only one. By looking in the IP routing table, we’ve seen that the lowest-cost metric for network 172.23.0.0 on R1 is 8576. This path goes through the 172.12.123.0 network. There is another valid path that uses the 172.12.13.0 network, but is not currently in use.

I 172.23.0.0/16 [100/8576] via 172.12.123.2, 00:00:53, Serial0

IGRP does not have a “show” command that displays all valid routes to a destination, as does EIGRP. The command debug ip igrp transactions will show the current metric of the routes using the 512 KBPS route.

R1#debug ip igrp transactions

IGRP protocol debugging is on

19:17:51: IGRP: broadcasting request on Loopback0

19:17:51: IGRP: broadcasting request on Serial0

19:17:51: IGRP: broadcasting request on Serial1

19:17:51: IGRP: received update from 172.12.13.3 on Serial1

19:17:51: subnet 172.12.13.0, metric 23531 (neighbor 21531)

19:17:51: subnet 172.12.123.0, metric 23531 (neighbor 8476)

19:17:51: network 1.0.0.0, metric 24031 (neighbor 8976)

19:17:51: network 2.0.0.0, metric 22131 (neighbor 1600)

19:17:51: network 3.0.0.0, metric 22031 (neighbor 501)

19:17:51: network 172.23.0.0, metric 21631 (neighbor 1100)

R1(config)#router igrp 1
R1(config-router)#variance 3
R1#show ip route 172.23.0.0
Routing entry for 172.23.0.0/16
Known via “igrp 1″, distance 100, metric 8576
Redistributing via igrp 1
Advertised by igrp 1 (self originated)
Last update from 172.12.123.2 on Serial0, 00:00:01 ago
Routing Descriptor Blocks:
* 172.12.13.3, from 172.12.13.3, 00:00:20 ago, via Serial1
Route metric is 21631, traffic share count is 1
Total delay is 21000 microseconds, minimum bandwidth is 512 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 0
172.12.123.3, from 172.12.123.3, 00:00:20 ago, via Serial0
Route metric is 8576, traffic share count is 3
Total delay is 21000 microseconds, minimum bandwidth is 1544 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 0
172.12.123.2, from 172.12.123.2, 00:00:01 ago, via Serial0
Route metric is 8576, traffic share count is 3
Total delay is 21000 microseconds, minimum bandwidth is 1544 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 0

The metric for 172.23.0.0 through the direct connection is 21631. A variance of 3 means that any route with a metric less than the best metric multiplied by the variance (in this case, 8576 x 3 = 25728) will be entered into the routing table. R1 now has three unequal-cost paths to 172.23.0.0 in its routing table, and load balancing will take place.

IGRP unequal-cost load balancing takes some practice, but as you can see, once you get the metric it’s easy to work with. Just make sure you know how to get that metric!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage, home of free CCNA and CCNP tutorials, The Ultimate CCNA Study Package, and Ultimate CCNP Study Packages.

You can also join his RSS feed and visit his blog, which is updated several times daily with new Cisco certification articles, free tutorials, and daily CCNA / CCNP exam questions! Details are on the website.

For a FREE copy of his latest e-books, “How To Pass The CCNA” and “How To Pass The CCNP”, visit the website and download your free copies. You can also get FREE CCNA and CCNP exam questions every day! Get your CCNA study guide from The Bryant Advantage!

Hurricane Study Strategies to Stacking Up Computer Certifications

Writen by Lance Winslow

In many parts of the country we find that people with computer certifications are more plentiful than in other parts of the country. Recently when I was doing a study of this demographic and looking at the data from a computer magazine I noticed that many people who lived in Florida and along the Gulf Coast had more computer certifications per individual than in other parts of the country.

In many parts the country there are severe shortages of people with computer certifications, while in other parts the country this is not as big a problem for large corporations. When studying this issue I determined that one of the problems was that in big cities like Dallas, Denver, Los Angeles, the Bay area, Maryland, Boston, Philadelphia, Chicago, Atlanta, and the D.C. area that shortages of people with computer certifications was a huge issue. While in Florida and along the Gulf Coast there were more people who had more certifications, than expected.

Perhaps this is because during hurricanes there is not a lot that people can do so they study for their computer certifications and this is a very good way to stack up computer certifications for someone wishing to have more of them. The more certifications you have the better chances you’ll have been getting the perfect job that you desire in the computer industry.

There is currently a shortage of IT people and a larger shortage is expected in the coming years. Please consider this in 2006 and study your butt off next time there is a hurricane that you are waiting to pass you.

Lance Winslow

Cisco CCNA Exam Tutorial: Cisco Discovery Protocol (CDP)

Writen by Chris Bryant

The Cisco Discovery Protocol (CDP) sure looks simple enough, but there are quite a few details to know for success on the CCNA exam. In your CCNP studies, you’ll be introduced to additional uses for CDP, but for now it’s enough to know that CDP is designed to give you information regarding directly connected Cisco routers and switches.

CDP runs by default between all directly connected Cisco devices. CDP is also a Cisco-proprietary protocol – if the directly connected device is not a Cisco device, you won’t see the information you wanted.

The basic CDP command to display information about the directly connected neighbor is “show cdp neighbor”.

R2#show cdp neighbor

Capability Codes: R – Router, T – Trans Bridge, B – Source Route Bridge

S – Switch, H – Host, I – IGMP, r – Repeater

Device ID Local Intrfce Holdtme Capability Platform Port ID

R1 BRI0 167 R 2521 Dialer1

This command is particularly helpful when troubleshooting Cisco switches. There’s no need to trace wiring in a rack of Cisco devices to see what routers are connected to a Cisco switch when show cdp neighbor can be used. In the above output, you can see the remote device’s hostname, what interface on the remote device is connected to the local device, the capability of the remote device, the remote device’s hardware platform, and the local interface that is connected to the remote device.

CDP can be disabled at both the global and interface level. To disable CDP at the interface level, run no cdp enable on the interface, and cdp enable to turn it back on.

cdp timer defines how often CDP packets are transmitted, and cdp holdtime defines how long a device will hold a received packet.

To turn CDP off for the entire router, run no cdp run. To view the current global status of CDP, run show cdp.

R2#show cdp

Global CDP information:

Sending CDP packets every 60 seconds

Sending a holdtime value of 180 seconds

CDP is running by default.

R2#conf t

R2(config)#cdp timer 45

R2(config)#cdp holdtime 100

The CDP timers are changed.

R2#show cdp

Global CDP information:

Sending CDP packets every 45 seconds

Sending a holdtime value of 100 seconds

The CDP values have been successfully changed. “show cdp interface” will give the timer information for each interface on the router.

R2#conf t

R2(config)#interface bri0

R2(config-if)#no cdp enable

CDP is disabled on the BRI interface. This does NOT have to be done to keep the line from dialing.

R2#conf t

R2(config)#no cdp run

CDP is disabled globally.

R2#show cdp

% CDP is not enabled

CDP has been successfully disabled.

Show cdp neighbor gives you a great deal of information, but what if you need the neighbor’s IP address? Just run show cdp neighbor detail. You will get even more information about that directly connected neighbor, including its IP address.

SW2#show cdp neighbor detail

————————-

Device ID: R4

Entry address(es):

IP address: 172.12.23.4

Platform: cisco 2520, Capabilities: Router

Interface: FastEthernet0/4, Port ID (outgoing port): Ethernet0

Holdtime : 158 sec

The details of CDP are important to you on the job and in the CCNA exam room. When you find yourself negotiating a badly documented network, you can use CDP to “walk” through the network and create a network map for your client as well. Sometimes the simplest protocols are the most helpful!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage, home of free CCNA and CCNP tutorials, The Ultimate CCNA Study Package, and Ultimate CCNP Study Packages.

You can also join his RSS feed and visit his blog, which is updated several times daily with new Cisco certification articles, free tutorials, and daily CCNA / CCNP exam questions! Details are on the website.

For a FREE copy of his latest e-books, “How To Pass The CCNA” and “How To Pass The CCNP”, visit the website and download your free copies. You can also get FREE CCNA and CCNP exam questions every day! Get your CCNA study guide from The Bryant Advantage!

An Introduction To MCSE Certification

Writen by Elizabeth Morgan

Microsoft certifications are one of the most popular and coveted certifications in the information technology industry today. There is great demand for Microsoft-trained professionals in the job market. Microsoft also offers many certification levels depending upon user proficiency and the nature of the job. One of the most popular certificates is the MCSE certificate.

Most IT professionals pursue MCSE training after they have gained experience in the industry. This enables them to implement their newly acquired skills in their jobs. The certification is ideal for anyone who wishes to design and implement infrastructure for business solutions in certain installations that use Microsoft Windows platforms. It also provides an edge to professionals already in the field, as the formal certification guarantees recognition by employers and scope for higher promotions.

Some people wishing to work in the industry also take the certification. This added tool provides a valuable benchmark for prospective employers to assess the skills of the candidate, and for the employee to negotiate for a competitive salary.

Microsoft offers different MSCE certifications for different users. There is the MSCE on Windows server 2003 and the MSCE on Microsoft Windows NT 4.0, and Windows 2000. There are specializations available for security and messaging on both servers 2003 and 2000. This is beneficial for employees of companies already working on these systems to enhance their skills.

Microsoft has independent requirements for the MSCE certification on the Windows 2000 platform and on Windows server 2003. For the certificate pertaining to the Windows 2000 platform one needs to clear five core examinations, four of which are based on the operating systems and one on design. There are two elective exams which help determine technical proficiency and the level of ease in solution design and implementation.

For the Windows server 2003 there are six core exams required, four of which are based on networking systems, one on client operating systems and one design exam. There is one elective examination similar in nature to the one for Windows 2000.

MCSE Certification provides detailed information on MCSE Certification, MCSE Certification Training, Online MCSE Certification, MCSE Certification Exam and more. MCSE Certification is affiliated with MCSE Term Papers.

An Overview of CompTIA Certification Programs

Writen by Natalie Aranda

High-tech is often associated with computers or information technology (IT). IT has transformed the way we live and the way we conduct businesses. A well-established certification program is often the indication of maturity of an industry or profession. The programs utilize standard tests to exam the knowledge and level of expertise of the professionals . CompTIA certifications are one of such certification programs for the information technology industry. CompTIA certifications are provided by The Computing Technology Industry Association (CompTIA) – a non-profit trade association founded in 1982. Many of ComPTIA certification exams are computer-based and are composed of multiple choice questions.

A+

The A+ certification demonstrates the knowledge and understanding of computer hardware and operating systems. It is primarily designed for qualification of a computer technician though many organization utilize the A+ certification training to help their employee to acquire the basic knowledge of computer hardware and operating systems.

The actual certification includes the A+ Hardware Exam and the A+ Operating System Technologies Exam, which focuses exclusively on Microsoft operating systems. The A+ exam is designed for IT professionals who have about a year of hands-on experience.

Network+

Network+ certification is designed for network technicians to test and demonstrates skill and understanding of network hardware, installation, and troubleshooting in general. Network+ certification is not vendor specific. Besides Network+ certification, network technicians further acquire vendor specific certification, such as to Microsoft certifications and Cisco certifications.

Server+

CompTIA Server+ certification demonstrate the competency of server-specific hardware and operating systems skills. A+/Server+ certification focus on the general knowledge of various servers while the Microsoft Certified Systems Administrator (MCSA) certification, of course, test the knowledge of Microsoft products – NT server, SQLServer or Information server for web publishing.

Security+

Security+ certification focus on security aspect of information technology, such computer security and network security.

Linux+

As the Open Source operation system gains the popularity and wide acceptance, CompTIA offers Linux+ certification. Unlike other CompTIA certifications which focus on general understanding of the subject, not on any vendor-specific products. Linux+ is product-specific, but not vendor-specific because the nature of open source software. The certification exam covers the installation, management, configuration, security, documentation, and hardware of Lunix.

The most-known ComPTIA certification is A+ certification for computer hardware and operating system. Many organizations simply utilize A+ training for general computer training. Other even less-known certifications from ComPTIA are HTI+ (Home Technology Integrator covers installation, integration and troubleshooting of automated home sub-systems; e-Biz+ certification covering basic knowledge of e-commerce, CTT+ certification for training professionals, and CDIA+ certification for document management and enterprise content management.

Cisco CCNA Certification: Error Detection vs Error Recovery

Writen by Chris Bryant

Passing the CCNA, Intro, and ICND exam is all about knowing and noticing the details. (Which makes perfect sense, since becoming a master networking administrator or engineer is also about noticing the details!) One such detail knows the difference between error detection and error recovery. While the terms are sometimes used interchangeably, they are not the same thing.

Error detection is just that – error detection only. Two common error detection methods are found at the Data Link layer of the OSI model, the FCS (Frame Check Sequence) and CRC (Cyclical Redundancy Check). A mathematical equation is run against the data in the frame, and the result is sent along with the data. The receiver runs the equation again, but this time. If the result is the same, the frame is considered valid; if the result is different, the frame is considered corrupt and is discarded.

Note that the FCS and CRC do nothing in regards to retransmission. They are strictly error detection schemes.

For an example of error recovery, we look to the Transport layer, where TCP runs. TCP performs reliable delivery, and the reason we call it “reliable” is that TCP uses sequence numbers to detect missing segments. If the sender determines from the sequence numbers that the remote host did not receive transmitted segments, the sender will retransmit the missing segments.

The key to keeping the terms straight in your head is to remember that while both error detection and error recovery both detect problems, only error recovery does anything about it. It’s also worth reading an exam question twice when you see either term!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage, home of free CCNA and CCNP tutorials, The Ultimate CCNA Study Package, and Ultimate CCNP Study Packages. For a FREE copy of his latest e-books, “How To Pass The CCNA” and “How To Pass The CCNP”, visit the website and download your free copies. You can also get FREE CCNA and CCNP exam questions every day! Pass the CCNA exam with The Bryant Advantage!

Cisco CCNA / CCNP Certification Exam Tutorial: Dialer Watch

Writen by Chris Bryant

Dialer Watch is a vital part of your CCNA and CCNP studies, particularly for the BCRAN exam, but it’s one of the most misunderstood technologies as well. To help you pass the CCNA and CCNP certification exams, here’s a detailed look at Dialer Watch.

Dialer Watch allows you to configure a route or routes as “watched” when the watched route leaves the routing table and there is no other valid route to that specific destination, the ISDN link will come up. In the following example, R1 and R2 are connected by both a Frame Relay cloud over the 172.12.123.0 /24 network and an ISDN cloud using the 172.12.12.0 /24 network. The routers are running OSPF over the Frame cloud, and R1 is advertising its loopback of 1.1.1.1/32 as well as an Ethernet segment, 10.1.1.0/24, via OSPF. R2 has both of these routes in its OSPF table, as shown below.

R2#show ip route ospf

1.0.0.0/32 is subnetted, 1 subnets

O 1.1.1.1 [110/65] via 172.12.123.1, 00:00:07, Serial0

10.0.0.0/24 is subnetted, 1 subnets

O 10.1.1.0 [110/128] via 172.12.123.1, 00:00:08, Serial0

We want R2 to place a call to R1 if either the loopback or Ethernet networks leave R2’s routing table, but we don’t want to have to depend on interesting traffic. That dictates the use of Dialer Watch.

First, configure the list of watched routes with dialer watch-list. Only one of the watched routes needs to leave the routing table for the ISDN link to come up. In this example, R2 will watch both routes from its OSPF routing table.

Be careful with this command. The entries here need to match exactly the routes and masks being watched. Dialer watch-lists use subnet masks, not wildcard masks.

R2(config)#dialer watch-list 5 ip 10.1.1.0 255.255.255.0

R2(config)#dialer watch-list 5 ip 1.1.1.1 255.255.255.255

Configure the dialer watch-group command on the BRI interface, AND frame map statements for the watched routes. As with dialer-list and dialer-group, the group number referenced in the dialer watch-group command must match the number assigned to the dialer watch-list.

The Dialer Watch configuration will not work without frame map statements for each watched route. I repeat this because this is the step a lot of people leave out.

R2(config)#interface bri0

R2(config-if)#dialer watch-group 5

R2(config-if)# dialer map ip 1.1.1.1 255.255.255.255. name R1 5557777 broadcast

R2(config-if)# dialer map ip 10.1.1.0 255.255.255.0 name R1 5557777 broadcast

To test Dialer Watch, the Serial0 interface on R2 will be shut down. Since we’re running OSPF, the route table will be updated almost immediately and the ISDN link should come up right after that.

R2(config)#int s0

R2(config-if)#shut

01:12:47: %OSPF-5-ADJCHG: Process 1, Nbr 1.1.1.1 on Serial0 from FULL to DOWN, N eighbor Down: Interface down or detached

01:12:47: %LINK-3-UPDOWN: Interface BRI0:1, changed state to up

01:12:48: %SYS-5-CONFIG_I: Configured from console by console

01:12:48: %LINEPROTO-5-UPDOWN: Line protocol on Interface BRI0:1, changed state to up

01:12:49: %LINK-5-CHANGED: Interface Serial0, changed state to administratively down

01:12:50: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state to down

01:12:53: %ISDN-6-CONNECT: Interface BRI0:1 is now connected to 5557777 R1

Within five seconds, the ISDN link is up. show dialer verifies that Dialer Watch is the reason the line was brought up.

R2#show dialer

BRI0 – dialer type = ISDN

Dial String Successes Failures Last DNIS Last status

5557777 2 0 00:00:11 successful

0 incoming call(s) have been screened.

0 incoming call(s) rejected for callback.

BRI0:1 – dialer type = ISDN

Idle timer (120 secs), Fast idle timer (20 secs)

Wait for carrier (30 secs), Re-enable (15 secs)

Dialer state is data link layer up

Dial reason: Dialing on watched route loss

Time until disconnect 108 secs

Connected to 5557777 (R1) A final note regarding Dialer Watch … it will not work with RIP, but will with all our other dynamic IGPs (IGRP, EIGRP, OSPF).

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage, home of free CCNA and CCNP tutorials, The Ultimate CCNA Study Package, and Ultimate CCNP Study Packages.

You can also join his RSS feed and visit his blog, which is updated several times daily with new Cisco certification articles, free tutorials, and daily CCNA / CCNP exam questions! Details are on the website.

For a FREE copy of his latest e-books, “How To Pass The CCNA” and “How To Pass The CCNP”, visit the website and download your free copies. You can also get FREE CCNA and CCNP exam questions every day! Get your CCNA study guide from The Bryant Advantage!