San Francisco on the Cheap

If you?ve ever visited San Francisco, you know it can be a very expensive city. Hotel costs, restaurant tabs, valet fees and cab fares can add up quite quickly. But, if you know where the values are, that trip to San Francisco can actually fit into your budget quite nicely.

First, let?s start with lodging. Yes, it?s nice to stay at the Grand Hyatt on Union Square or the Mark Hopkins. But, let?s face it, they?re expensive. For budget considerations, I suggest you consider Lombard Street. No, not the crooked part of Lombard Street, but the section of Lombard Street which runs through the Cow Hollow and Marina districts in the northern part of San Francisco, near the Golden Gate Bridge.

You can find a nice room on Lombard Street for just under $100 a night, which is a far cry from the hotels on Union Square. But, what kind of room will your $100 get you? Of course, you?re not going to get the luxury of a fancy hotel, but you?re not paying for luxury. You?re paying to enjoy San Francisco. Your $100 will buy you a comfortable, clean room. Also, you will generally receive free parking. If you drive to San Francisco or rent a car in San Francisco, free parking is a big deal. The luxury hotels usually charge for parking, as well as a in & out fees when you retrieve your car for a day trip or night out.

Lombard Street is also a great location. Just north of Lombard Street is Chestnut Street, with a movie theater, shops and wonderful food. To the south a few blocks you?ll find Union Street, with upscale shops and, again, wonderful food. Lombard Street is also a good location for bus service to all parts of San Francisco, eliminating the need for expensive taxi rides.

You have numerous choices for lodging along Lombard Street. I?ve stayed at the Cow Hollow Motor Inn (415-921-5800) and find it to be good, inexpensive choice, with free parking, with a nice, inexpensive Italian restaurant located just north on Steiner Street (Ristorante Parma). One caveat I have about Cow Hollow, which can probably be applied to any of the motels on Lombard Street, is that you will probably want to request an inside room off the main streets, as they can get quite loud. Another motel you might consider would be La Luna Inn (415-346-4664), a recently renovated inn with some luxuries you wouldn?t expect from a budget motel, such as pillow-top mattresses, flat screen TVs, wireless internet access and complimentary muffins, breads, coffee, tea and juices served every morning. All that for just under $100 per night for a single king or queen bed.

Restaurants can also add up to the cost of a vacation. San Francisco has a large amount of wonderful restaurants at inexpensive prices. Of course, you have to know which ones they are. Those would usually be the ones the locals frequent, so if you want to avoid over-priced restaurants, you?d stay away from restaurants in tourist traps like Fisherman?s Wharf and go for neighborhood restaurants, such as those found in Cow Hollow and the Marina District, 24th Street in Noe Valley, or Potrero Hill. One very inexpensive restaurant I?d recommend in Potrero Hill is San Francisco Bar B Que, 1328 18th St., a wonderful little Thai BBQ restaurant that serves great food at cheap prices. If there?s a wait, just put your name on the list and bop into Bloom?s Saloon a couple doors down for a drink and great views of the downtown skyline.

As for inexpensive things to do in San Francisco, check out the free walking tours offered by San Francisco City Guides, a non-profit organization of more than 200 trained volunteers who lead free walking tours in San Francisco. Their website at sfcityguides.org lists all the many different walking tours of such sites as Chinatown, Golden Gate Bridge, Coit Tower, and even ghost walks of supposedly haunted locations.

San Francisco is truly a great city to visit. It?s even better when you know you can visit and experience all the city has to offer without breaking the bank.

Shari Hearn is a writer and creator of Top Vacation Spots, where you can learn more about things to do in San Francisco.

 

San Francisco Plastic Surgeon offers most advanced silicone breast implant option

San Francisco, CA November 20, 2006 -- Following the United States Food and Drug Administration?s approval on Friday November 17th 2006 of silicone breast implants for use in cosmetic breast augmentation surgery, San Francisco Board-Certified Plastic Surgeon Dr. Scott W. Mosser, will begin immediately offering the newly approved implants as an option for all his patients seeking this type of cosmetic surgery.

This is good news for Bay Area women who may be considering breast augmentation. They now can consider silicone implants in addition to the commonly used saline filled implants currently being used for cosmetic surgery.

Dr. Mosser, who specializes in breast surgery, has used the improved silicone implants for some time for reconstructive breast surgery following mastectomy and for corrective surgery for medical reasons. The FDA?s 14-year ban on silicone implants did not extend to their use in breast augmentation surgery for medical reasons. He now anticipates a greatly increased demand for cosmetic reasons.

In announcing the approval, the FDA stated, "The extensive body of scientific evidence provides reasonable assurance of the benefits and risks of these devices. This information is available in the product labeling and will enable women and their physicians to make informed decisions."

This newer form of silicone implants ? with a thicker, cohesive gel ? has been widely used in the US for some time for breast surgery designated as ?reconstructive?; that is, anything from breast lifts combined with implants to post-cancer restoration.

The new silicone implant gel technology is cohesive, which means that it defies diffusion when rupture occurs, behaving more like a viscous gel than a liquid. Would a leak to happen, this material is designed to be less likely to seep into local tissues and cause inflammation.

The FDA approved the implants for use in cosmetic surgery on women over the age of 22 after carefully reviewing safety data over the past decade. The FDA has also stipulated that the manufacturers must continue follow up safety studies. As a condition of the implants' approval, each company agreed to conduct a study tracking 40,000 women for ten years after receiving silicone implants and must also continue lab studies on implant failures.

This development, coupled with recent studies disproving any link between silicone implants and systemic disease, have now lessened the fear and greatly broadened the options available to any woman seeking cosmetic breast augmentation.

Now that women have the added option of using silicone, each qualified breast augmentation candidate has the additional responsibility of understanding the pros and cons of silicon vs. saline, cautions Dr. Mosser. ?The decision of whether to use saline or silicone implants is still one which should be made by a Board-Certified Plastic Surgeon and should be tailored specifically to the individual patient. Every patient is unique and the choice of type of implant and surgical procedure used is a very personal and carefully weighed decision.?

In addition to understanding implant options, one of the most important questions to ask when you are researching breast augmentation surgeons, in order to make a responsible decision, is the surgeon?s qualification. Any licensed physician can legally advertise him/herself as a plastic or cosmetic surgeon. Therefore, choosing a board certified plastic surgeon for a breast augmentation can help prevent complications and reduce the risks already involved. Patients who choose a board certified plastic surgeon can be assured that quality training and prestigious credentials are available.

Dr. Mosser also advises breast augmentation candidates to ask the following questions while researching plastic surgeons in order to determine if he or she is able to perform the procedure at a high level of safety, with desirable results:

-How many breast augmentations have you performed?
-Are the goals I wish to achieve attainable?
-What are the risks involved?
-How long is the recovery period before I can expect to see the final results?
-What happens if I am dissatisfied with the results?

Following the FDA approval of silicone breast implants for cosmetic augmentation on November 17th, a Board Certified San Francisco Plastic Surgeon offers a perspective on responsible, individualized patient decisions.

How to: Cisco 2600 Router's Password Recovery

As you might already know, the configuration register value is the key player in password recovery. This is due to the fact that the configuration register value controls the boot sequence. The part that matters in the configuration register here is the sixth bit. When this bit is off, the router look into the NVRAM for the configuration. If the bit is on, the router neglects the contents of NVRAM and acts as if there is no (startup-config). So, to get things going when you have forgotten the password, or a previous administrator does not give you the password due to lack of documentation, you can bypass this problem.

Go through the following steps carefully:

1. Interrupt the router booting operation. This is done by pressing (Ctrl+Break) key simultaneously as soon as you turn on the router. This step will get you to the ROM monitor mode (rommon).

You will have the following:

System Bootstrap, Version 11.3(2)XA4, RELEASE SOFTWARE (fc1)

Copyright (c) 1999 by cisco Systems, Inc.

TAC:Home:SW:IOS:Specials for info

PC = 0xfff0a530, Vector = 0x500, SP = 0x680127b0

C2600 platform with 32768 Kbytes of main memory

PC = 0xfff0a530, Vector = 0x500, SP = 0x80004374 monitor:

command "boot" aborted due to user interrupt

rommon 1 >

The (rommon 1 >) prompt is for the ROM monitor mode.

2. Now you should change the value of the configuration register in order to make the router neglect the contents of the NVRAM in the next boot up. This is achieved using the following command:

rommon 1 > confreg 0x2142

This command will change the sixth bit (originally the configuration register is 0x2102) to one. By doing so, the router will act as new in the next boot.

3. Perform a restart to the router using the following command:

rommon 1 > reset

4. The router now will restart and ask you if you want to use the setup mode and of course you will say no. Now, in order not to loose the configuration that you already have in the router, you should go to the USER privileged mode and perform:

Router#copy start run

This will get you back your old configuration but with one exception, you already are in the privileged mode without having to know the password..!!!!

Now you put a new password or passwords if you may:

Router(config)#enable secret blabla

And you can also put new console and telnet passwords if you like.

5. To get things going back to normal, change the value of the configuration register to its original form (0x2102) using the following global configuration command:

Router(config)#config-register 0x2102

6. Now you should save the configuration including the new passwords that you know:

Router#copy run start

7. Now reload and you are good to go:

Router#reload

What we have done in these steps is that we by passed the original configuration that has the unknown password, and then we got to the privileged mode without the need to know the password. And then we loaded the old configuration so we don?t loose it and imposed a new password and saved things back to the NVRAM. And then we got back to the original boot sequence. A piece of cake, isn?t it??

Cisco CCNA Certification Training Tutorial: PPP Multilink And ISDN BRI

Earning your CCNA certification means you have to notice details about Cisco routers that others might miss, and that's true in the exam room and on the job. In today's tutorial, we'll take a look at multilink PPP - a topic that seems simple enough, but has details that trip up some CCNA certification candidates.

ISDN BRI (Basic Rate Interface) has two B-channels that both carry data, and they each have a capacity of 64 KBPS. Interestingly enough, they don't share the load by default - the first channel has to be at capacity before the second channel starts taking some of the load. It's more efficient to have the channels share the load before then, and we can do just that by configuring PPP multilink. (Note that it's called PPP multilink for a reason. We can't configure it if the BRI interface is running at the default of HDLC.)

Configuring PPP multilink is simple enough. PPP must be running on the interface to begin with, and then you simply configure the interface with the "PPP multilink" command.

R1(config)#int bri0

R1(config-if)#encapsulation ppp

R1(config-if)#ppp multilink

Here's where knowing the details comes in handy. An additional command, "dialer load-threshold", is needed to define the capacity level of the first b-channel that will bring up the second b-channel. For example, let's say we want the second channel to come up when the first channel hits 50% of its capacity. It's easy to think that we would put "50" at the end of the dialer load-threshold command, but that's wrong! Look at what IOS Help tells us about this command.

R1(config-if)#dialer load-threshold ?

<1-255> Load threshold to place another call

This value is based on 255, not 100. To bring the second channel up as described earlier, we need to enter a value that is 50% of 255:

R1(config-if)#dialer load-threshold 127

The dialer load-threshold command has other options not shown here. The interface can be configured to consider only incoming or outgoing traffic for this command, or both.

This is just one of the many details you must master in order to earn your CCNA certification. Take it from me - it's worth it. Keep studying!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage, home of over 100 free certification exam tutorials, including CCNA certification training articles. His exclusive CCNA study guide is also available!

Visit his blog and sign up for Cisco Certification Central, a daily newsletter packed with CCNA, Network+, Security+, A+, and CCNP certification exam practice questions! A free 7-part course, ?How To Pass The CCNA?, is also available, and you can attend an in-person or online Cisco CCNA training boot camp with The Bryant Advantage!

Learn to Salsa Dance San Francisco Style!

Learn to salsa dance in the most beautiful part of San Francisco!

Learn how to salsa dance with experienced instructors and be able to enjoy the cities hottest nightlife. The salsa dance circuit has taken San Francisco by storm. Now you can be a part of it by taking the Dance SF salsa dance classes! Find out more by visiting www.dancesf.com!

These classes are suitable for absolute beginners but there are also intermediate classes available for students that already have experience in salsa dance and know the basics taught in the beginner's class.

Group classes at the beginner and intermediate levels of salsa start on a monthly basis. But the best part of these classes is that they are held at locations throughout the San Francisco Bay Area, which makes accessibility easy for everyone!

Each salsa dance class session is four weeks long, and they are progressive classes that meet once a week - usually on Wednesdays. These classes are for everyone. No partner and no experience are necessary! Drop-ins are accepted ($15 drop-in fee). Register On-line, and save money! Go to www.DanceSF.com

The salsa dance class is taught by Tianne Frias who danced for nine years with the acclaimed Robert Moses' KIN. In her earlier dance careers she started with Argentine Tango. Later, her interest spread to all the ballroom dances... now with an emphasis on Club-Style Salsa.

Tianne is trained in modern dance, ballroom, ballet and yoga, which have given her the natural flare for salsa dance. Having taught and performed internationally she has many years of experience. At the European Round Dance Festival, her students had commented, "Tianne's enthusiasm and love of dance took hold of the group and was reflected in three intense and enjoyable training sessions." Tianne has a natural love for dance and it shows in her classes.

To join these highly acclaimed classes, sign up by visiting the website at http://www.DanceSF.com

Or you can call or email for more information at: info@dancesf.com or 415-668-9936

Sign up and get dancing!

Evan Margolin is the president of DanceSF, the premiere salsa dancing academy in the San Francisco Bay Area. Learn to dance at the studio or in your own home with his Learn to Salsa DVDs. Find out more by visiting http://www.DanceSF.com

Cisco CCNP / BSCI Exam Tutorial: 10 ISIS Details You Must Know!

Earning your CCNP certification and passing the BSCI exam depends on knowing the details of many Cisco technologies, ISIS chief among them. To help you prepare for exam success, here's a list of ISIS terminology and basic concepts that will help you pass this tough exam. Enjoy!

ISIS Terms:

Domain: section of the network under common administrative control

Area: logical segment of the network composed of contiguous routers and their data links

Intermediate System: A router.

End System: A host device.

The four levels of ISIS routing:

Level 0: ES-IS routing in the same subnet.

Level 1: IS-IS routing in the same area.

Level 2: IS-IS routing in the same domain.

Level 3: Inter-domain routing performed by InterDomain Routing Protocol (IDRP).

ISIS Adjacency Possibilities:

L1: Can form adjacency with any L1 in the same area and any L1/L2 in the same area.

L2: Can form adjacency with any L2 in any area, and with an L1/L2 in any area.

L1/L2: Can form adjacency with any L1 in the same area, L1/L2 in any area, and L2 in any area.

A router interface's SNPA (Subnetwork Point Of Attachment) is its highest DLCI number if it's on a Frame network, and its MAC address if the interface is on an Ethernet segment.

ISIS Hello Types:

ESH: ES Hello - Sent by End Systems to discover a router.

ISH: IS Hello - Send by Intermediate Systems to announce their presence. End Systems listen for these.

IIH: IS-to-IS Hello - Send by one IS to be heard by another IS. These hellos makes IS-IS adjacencies possible.

Best of luck on your CCNP exams!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage , home of free CCNA and CCNP tutorials! Pass the CCNP exam with Chris Bryant!

Cisco CCNP Certification / BCMSN Exam Tutorial: The HSRP MAC Address

To pass the BCMSN exam and earn your CCNP, you've got to know HSRP inside and out! Part of that is knowing how the MAC address of the virtual router is derived, and another part is knowing how to change this address. We'll look at both features in this tutorial.

We've got two routers on a segment running HSRP, so first we need to find out what the MAC address of the HSRP virtual router is. The show command for HSRP is show standby, and it's the first command you should run while configuring and troubleshooting HSRP. Let's run it on both routers and compare results.

R2#show standby

Ethernet0 - Group 5

Local state is Standby, priority 100

Hellotime 3 sec, holdtime 10 sec

Next hello sent in 0.776

Virtual IP address is 172.12.23.10 configured

Active router is 172.12.23.3, priority 100 expires in 9.568

Standby router is local

1 state changes, last state change 00:00:22

R3#show standby

Ethernet0 - Group 5

Local state is Active, priority 100

Hellotime 3 sec, holdtime 10 sec

Next hello sent in 2.592

Virtual IP address is 172.12.23.10 configured

Active router is local

Standby router is 172.12.23.2 expires in 8.020

Virtual mac address is 0000.0c07.ac05

2 state changes, last state change 00:02:08

R3 is in Active state, while R2 is in Standby. The hosts are using the 172.12.123.10 address as their gateway, but R3 is actually handling the workload. R2 will take over if R3 becomes unavailable.

An IP address was statically assigned to the virtual router, but not a MAC address. However, there is a MAC address under the show standby output on R3, the active router. How did the HSRP process arrive at a MAC of 00-00-0c-07-ac-05?

Well, most of the work is already done before the configuration is even begun. The MAC address 00-00-0c-07-ac-xx is reserved for HSRP, and xx is the group number in hexadecimal. That's a good skill to have for the exam, so make sure you're comfortable with hex conversions. The group number is 5, which is expressed as 05 with a two-bit hex character. If the group number had been 17, we'd see 11 at the end of the MAC address - one unit of 16, one unit of 1.

On rare occasions, you may have to change the MAC address assigned to the virtual router. This is done with the standby mac-address command. Just make sure you're not duplicating a MAC address that's already on your network!

R2(config-if)#standby 5 mac-address 0000.1111.2222

1d12h: %STANDBY-6-STATECHANGE: Ethernet0 Group 5 state Active -> Learn

R2#show standby

Ethernet0 - Group 5

Local state is Active, priority 150, may preempt

Hellotime 4 sec, holdtime 12 sec

Next hello sent in 3.476

Virtual IP address is 172.12.23.10 configured

Active router is local

Standby router is 172.12.23.3 expires in 10.204

Virtual mac address is 0000.1111.2222 configured

4 state changes, last state change 00:00:00

1d12h: %STANDBY-6-STATECHANGE: Ethernet0 Group 5 state Listen -> Active

The MAC address will take a few seconds to change, and the HSRP routers will go into Learn state for that time period.

A real-world HSRP troubleshooting note: If you see constant state changes with your HSRP configuration, do what you should always do when troubleshooting - check the physical layer first. Best of luck on your BCMSN exam!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage , home of free CCNA and CCNP tutorials! Pass the CCNA exam with Chris Bryant

Cisco CCNA Certification Exam Tutorial: Distance Vector Command Review

Part of studying for CCNA exam success is keeping all these new commands straight in your head! And let's face it, there are a lot of commands you need to know in order to pass the CCNA exam and earn that certification. Here's a review of some very important distance vector and static routing commands you need to know, along with their proper usage and console output.

Bandwidth IGRP makes a default assumption that any Serial interface running IGRP is connected to a T1 line, which runs at 1544 KBPS. With equal-cost load-balancing enabled by default, this may be an undesirable assumption.

To alter IGRP's assumption, use the bandwidth command on the serial interface in question. Note that this command does NOT actually affect the bandwidth available to the interface; it merely changes IGRP's assumption of the bandwidth. R2#conf t

R2(config)#int s0

R2(config-if)#bandwidth 512

Clear ip route *

This command clears your routing table of all non-static and non-connected routes. In a lab environment, it's very handy because it forces your routers running routing protocols to send and request updates, rather than waiting for the regularly scheduled updates. R2#clear ip route *

Debug ip igrp events

Debug ip igrp events allows you to see IGRP updates being sent and requested. Here, the debug is run and then the routing table is cleared. The router immediately broadcasts update requests via the IGRP-enabled interfaces.

R2#debug ip igrp event

IGRP event debugging is on

R2#clear ip route *

06:02:51: IGRP: broadcasting request on BRI0

06:02:51: IGRP: broadcasting request on Serial0.123

Debug ip igrp transactions

To configure IGRP unequal-cost load-sharing with the variance command, you've got to know the metric of the less-desirable routes. EIGRP keeps these in its topology table; IGRP has no such table.

To get the metrics of routes not in the routing table, run debug ip igrp transactions. To force IGRP updates, the routing table below was cleared with clear ip route *.

R2#debug ip igrp transactions

IGRP protocol debugging is on

R2#clear ip route *

06:05:33: IGRP: received update from 172.12.123.1 on Serial0.123

06:05:33: subnet 172.12.123.0, metric 10476 (neighbor 8476)

06:05:33: network 1.0.0.0, metric 8976 (neighbor 501)

06:05:33: IGRP: edition is now 3

06:05:33: IGRP: sending update to 255.255.255.255 via BRI0 (172.12.12.2)

06:05:33: network 1.0.0.0, metric=8976

06:05:33: IGRP: sending update to 255.255.255.255 via Serial0.123 (172.12.123.2) - suppressing null update

06:05:34: IGRP: received update from 172.12.12.1 on BRI0

06:05:34: subnet 172.12.13.0, metric 160250 (neighbor 8476)

06:05:34: network 1.0.0.0, metric 158750 (neighbor 501)

Debug ip rip

R2#debug ip rip

IP protocol debugging is on

R2#clear ip route *

6:14:53: RIP: received v2 update from 172.23.23.3 on Ethernet0

6:14:53: 1.0.0.0/8 via 0.0.0.0 in 16 hops (inaccessible)

6:14:53: 1.1.1.1/32 via 0.0.0.0 in 2 hops

6:14:53: 172.12.0.0/16 via 0.0.0.0 in 16 hops (inaccessible)

6:14:53: 172.12.12.2/32 via 0.0.0.0 in 2 hops

6:14:53: 172.12.13.0/30 via 0.0.0.0 in 1 hops

6:14:53: 172.12.123.0/24 via 0.0.0.0 in 1 hops

6:14:53: 172.23.0.0/16 via 0.0.0.0 in 16 hops (inaccessible)

Run debug ip rip to troubleshoot routing update problems, RIP authentication problems, and to view the routing update contents. Clear ip route * was run to clear the routing table and to force a RIP update.

Ip route R2#conf t

R2(config)#ip route 1.1.1.1 255.255.255.255 172.12.123.1

OR

R2(config)#ip route 1.1.1.1 255.255.255.255 serial0

To configure a static route to a given destination IP address, use the ip route command. The destination is followed by a subnet mask, and that can be followed by either the next-hop IP address or the exit interface on the local router.

Ip route 0.0.0.0 0.0.0.0

R2#conf t

R2(config)#ip route 0.0.0.0 0.0.0.0 172.12.123.1

OR

R2(config)#ip route 0.0.0.0 0.0.0.0 ethernet0

To configure a default static route, use either of these two commands.

You could have any number for the first "0.0.0.0", since the second set of zeroes is the subnet mask. This means that any destination will match this route statement.

That's a good review to get started with! I'll be back tomorrow with Part II of this CCNA exam command review!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com), home of free CCNA and CCNP tutorials! For my FREE "How To Pass The CCNA" or "CCNP" ebook, visit the website and download your copies. Get your CCNA study guide from The Bryant Advantage!

The Brief History of Cisco Certifications

Even young people can remember the old days when network administrators were more often associated for being the person sitting next to a computer system rather than for specific abilities of proficiency. In those early days, CCNA Certification or CCNA training were concepts totally ignored by most small-to-medium businesses, and they never asked a network administrator to apply for a CCNA course.

In fact during long time, many office managers just learned a few computer tricks to qualify as network administrator because a Cisco Certified Network Associate (CCNA) was only known as inter networking became more complex. The increasingly sophistication in design and equipment requiring IT professionals.

CCNA training begin to be considered essential when the business world found that only the labor of a pool consisting of qualified technicians could handle common problems and new challenges resulting from the evolving of new technologies. A CCNA course was synonym of the knowledge and skills accrediting IT personal.

As the time went by, all major vendors of computer software and hardware started to develop their own certification programs with the customers in mind. CCNA Certification become necessary to ensure providing them with people up to date with the technology, to help customers implement their products.

This way, Cisco certifications began with the offer of the Cisco Certified Inter networking Engineer (CCIE), which was a extremely difficult level of certification, as the only CCNA course available during that time. Such CCNA Certification usually required several years of experience and thousands of dollars.

CCNA training consisted of torturous lab practical, needing multiple attempts at the exam, in order to pass. CCIE Certification still require the same level of experience, practice and the rigorous nature of the exam that only a few candidates actually pass, but Cisco has developed intermediate levels of certification nowadays.

CCNA Certification can be acquired applying for a CCNA course designed for those who want to be identified as Cisco-knowledgeable technicians to improve their opportunities to develop an IT career or integrate themselves to the growing demand for computer-related jobs.

It is a well known fact that a college degree in any field cannot guarantee employment, if the person holding a college diploma is not capable of doing properly the job, regardless any advanced degree. In networking, a traditional college four-year degree in Computer Science may be obsolete by graduation day due the constantly shifting nature of technology.

Cisco has worked very hard through its history to make sure any CCNA Certification, CCNA training or CCNA course retain its real worth and prestige in the marketplace.

Natalie Aranda writes about computer, technology and IT training.

Cisco CCNA Exam Tutorial: Split Horizon And Hub-And-Spoke Networks

For CCNA exam success, you had better know what split horizon is, how to turn it off, and when to turn it off. Knowing when to turn split horizon off is also important in production networks, because it can cause a hub-and-spoke network to have incomplete routing tables on the spokes.

Split horizon exists for a very good reason - routing loop prevention. The rule of split horizon states that a router cannot send an advertisement for a route out the same interface that it came in on. Split horizon is on by default on all interfaces running RIP, IGRP, and EIGRP.

In this CCNA tutorial, R1 will serve, as the hub and R2 and R3 will be the spokes. We'll first configure EIGRP over the 172.16.123.0 /24 network, the network connecting the three routers.

R1#conf t

R1(config)#router eigrp 100

R1(config-router)#no auto-summary

R1(config-router)#network 172.12.123.0 0.0.0.255

R2#conf t

R2(config)#router eigrp 100

R2(config-router)#no auto-summary

R2(config-router)#network 172.12.123.0 0.0.0.255

R3#conf t

R3(config)#router eigrp 100

R3(config-router)#no auto-summary

R3(config-router)#network 172.12.123.0 0.0.0.255

Running show ip eigrp neighbor on R1 shows that adjacencies to R2 and R3 are up.

R1#show ip eigrp neighbor

IP-EIGRP neighbors for process 100

H Address Interface Hold Uptime SRTT RTO Q Seq Type

(sec) (ms) Cnt Num

1 172.12.123.3 Se0/0 11 00:02:45 1 5000 0 1

0 172.12.123.2 Se0/0 161 00:03:01 1 5000 0 1 Each router will now advertise its loopback address via EIGRP.

R1#conf t

R1(config)#router eigrp 100

R1(config-router)#network 1.1.1.0 0.0.0.255

R2#conf t

R2(config)#router eigrp 100

R2(config-router)#network 2.2.2.0 0.0.0.255

R3#conf t

R3(config)#router eigrp 100

R3(config-router)#network 3.3.3.0 0.0.0.255

Running show ip eigrp route on each router shows that R1 has a route for both R2's and R3's loopback. R2 and R3 will only see R1's loopback address, and not each other's. Why?

R1#show ip route eigrp

2.0.0.0/24 is subnetted, 1 subnets

D 2.2.2.0 [90/2297856] via 172.12.123.2, 00:03:19, Serial0/0

3.0.0.0/24 is subnetted, 1 subnets

D 3.3.3.0 [90/2297856] via 172.12.123.3, 00:03:04, Serial0/0

R2#show ip route eigrp

1.0.0.0/24 is subnetted, 1 subnets

D 1.1.1.0 [90/2297856] via 172.12.123.1, 00:03:40, Serial0/0.123

R3#show ip route eigrp

1.0.0.0/24 is subnetted, 1 subnets

D 1.1.1.0 [90/2297856] via 172.12.123.1, 00:05:17, Serial0/0.31

EIGRP uses Split Horizon by default to prevent routing loops. In this lab, though, it prevents full network reachability. R2 and R3 both form neighbor relationships with R1's Serial physical interface. R2 advertises its loopback address to R1's Serial interface, as does R3. Split Horizon does not allow a route to be advertised back out the same interface it was received on. This prevents R1 from advertising R2's loopback to R3, or R3's loopback to R2.

Split Horizon must be disabled to allow full network reachability in this lab. To do so, run no ip split-horizon eigrp 100 on R1's Serial interface. When Split Horizon is disabled, that will cause the neighbor relationships to fail, and then reestablish. Run show ip route eigrp 100 on both R2 and R3. The appropriate route to the remote loopback address will now appear.

R1#conf t

R1(config)#int serial0

R1(config-if)#no ip split-horizon eigrp 100

10:02:23: %DUAL-5-NBRCHANGE: IP-EIGRP 100: Neighbor 172.12.123.2 (Serial0/0) down: split horizon changed

10:02:23: %DUAL-5-NBRCHANGE: IP-EIGRP 100: Neighbor 172.12.123.3 (Serial0/0) down: split horizon changed

10:02:27: %DUAL-5-NBRCHANGE: IP-EIGRP 100: Neighbor 172.12.123.3 (Serial0/0) ip: new adjacency

10:02:54: %DUAL-5-NBRCHANGE: IP-EIGRP 100: Neighbor 172.12.123.2 (Serial0/0) ip: new adjacency

R2#show ip route eigrp

1.0.0.0/24 is subnetted, 1 subnets

D 1.1.1.0 [90/2297856] via 172.12.123.1, 00:00:06, Serial0/0.123

3.0.0.0/24 is subnetted, 1 subnets

D 3.3.3.0 [90/2809856] via 172.12.123.1, 00:00:06, Serial0/0.123

R3#show ip route eigrp

1.0.0.0/24 is subnetted, 1 subnets

D 1.1.1.0 [90/2297856] via 172.12.123.1, 00:00:12, Serial0/0.31 2.0.0.0/24 is subnetted, 1 subnets

D 2.2.2.0 [90/2809856] via 172.12.123.1, 00:00:12, Serial0/0.31

Disabling split horizon should be done with care, but knowing when and where to do so shows that you truly understand how this technology works - and that's a big step on the way to earning your CCNA!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage , home of free CCNA and CCNP tutorials! Pass the CCNA exam with Chris Bryant!

Cisco CCNA Exam Tutorial: Loopback Interfaces

As a CCNA candidate, you most likely have some background in PC hardware and workstation support. If so, you're already familiar with loopback interfaces, particularly 127.0.0.1, the loopback address assigned to a PC.

When you're learning all about the different physical interfaces for your CCNA exam - serial, ethernet, and BRI, among others - there's one logical interface you need to know about, and that is - you guessed it! - the loopback interface.

What isn't as immediately apparent is why we use loopback interfaces on routers and switches to begin with. Many of the Cisco router features that can use loopbacks are intermediate and advanced features that you'll learn about in your CCNP and CCIE studies, but these features all come back to one basic concept: If the loopback interface on a router is down, that means the router is unavailable as a whole.

In contrast, a physical interface being down does not mean the router itself is out of commission. A router's ethernet port can go down, but the other physical interfaces on that router are still operational. Since a loopback interface is logical, there's nothing physical that can go wrong with it.

As I mentioned, you'll learn different Cisco router and switch features that utilize loopback interfaces as you climb the Cisco certification ladder. There's one misconception about Cisco loopback interfaces that you want to get clear on now, though. You?re probably familiar with loopback interfaces on a PC, and may even know that the address range 127.0.0.0 is reserved for loopback addressing.

Note that this reserved address range does not apply to loopbacks on Cisco devices, however. If you attempt to assign an address from this range to a Cisco loopback interface, you get this result:

R1#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R1(config)#interface loopback0

R1(config-if)#ip address 127.0.0.2 255.255.255.0

Not a valid host address - 127.0.0.2

R1(config-if)#ip address 127.1.1.1 255.255.255.0

Not a valid host address - 127.1.1.1

The range 127.0.0.0 is reserved for host loopbacks (such as PCs), not routers or switches. The most commonly used address from this range is 127.0.0.1 ? if you can?t ping that on a workstation, that means you can?t ping yourself, which means there?s a problem with the TCP/IP install itself.

Keep these details in mind on the exam and in the workplace, and you?re on your way to CCNA exam success!
Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com ), home of free CCNA and CCNP tutorials, and The Ultimate CCNA and CCNP Study Packages. For a copy of his FREE "How To Pass The CCNA" or "CCNP" ebook, visit the website and download copies! Our new RSS feed gives you free Cisco questions daily!

Cisco CCNA Certification Exam Tutorial: The OSPF RID

OSPF is a major topic on your CCNA exam, as well it should be. OSPF is a widely-used WAN protocol, and you need to learn the fundamentals before moving on to more complicated configurations. One such detail is the OSPF Router ID, or RID.

The RID is the dotted decimal value by which other OSPF routers will identify a given OSPF router. There are some interesting defaults for this value, and a command you should know to hardcode the RID. You had also better know what has to happen for this command to take effect, so let's take a more detailed look at the OSPF RID.

In this example, R1 has an adjacency with R2 and R3 over the 172.12.123.0/24 frame network. R1 is the hub, with R2 and R3 as the spokes. No other interfaces are OSPF-enabled on any of the routers. Running show ip ospf neighbor on R1, we see some unusual values under "Neighbor ID", which is another name for the OSPF RID.

R1#show ip ospf neighbor

Neighbor ID Pri State Dead Time Address Interface

3.3.3.3 0 FULL/DROTHER 00:01:57 172.12.123.3 Serial0

2.2.2.2 0 FULL/DROTHER 00:01:57 172.12.123.2 Serial0

When determining the Router ID (RID) of an OSPF-enabled router, OSPF will always use the numerically highest IP address on the router's loopback interfaces, regardless of whether that loopback is OSPF-enabled.

What if there is no loopback? OSPF will then use the numerically highest IP address of the physical interfaces, regardless of whether that interface is OSPF-enabled.

BOTTOM LINE: An interface does not have to be running OSPF to have its IP address used as the OSPF RID.

The OSPF RID can be changed, but it requires a restart or to reinitialize the OSPF routing process. Use the router-id command to change the default RID of each router as shown, and clear the OSPF process to do so.

R1#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R1(config)#router ospf 1

R1(config-router)#router-id 11.11.11.11

Reload or use "clear ip ospf process" command, for this to take effect

R1#clear ip ospf process

Reset ALL OSPF processes? [no]: yes

1d05h: %OSPF-5-ADJCHG: Process 1, Nbr 3.3.3.3 on Serial0 from 2WAY to DOWN, Neighbor Down: Interface down or detached

1d05h: %OSPF-5-ADJCHG: Process 1, Nbr 2.2.2.2 on Serial0 from 2WAY to DOWN, Neighbor Down: Interface down or detached

After entering the router-id command, the router console informed you that you have to reload the router or reset the OSPF processes for this to take effect. You enter the clear ip ospf process command to do this. Notice that when you're asked if you really want to do this, the prompt is "no"? That's because all the OSPF adjacencies on this router will be lost and will have to begin the process again. That's OK on a practice rack, not good in a production network. Don't use that one at work.

The OSPF RID is not a complicated concept, but the fact that an interface doesn't have to be OSPF-enabled in order to have its IP address act as the RID takes some getting used to. And remember - when the router or switch asks you a question and the prompted answer is "no", take one step back and make sure you really want to do what you're about to do!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com), home of free CCNA and CCNP tutorials! For my FREE "How To Pass The CCNA" or "CCNP" ebook, visit the website and download your copies. Get your CCNA study guide from The Bryant Advantage!