Interview questions for fresher network engineer: Tips and Tricks for CCNA, CCNP, OSPF, BGP, MPLS-VPN | Ask all your queries online absolutely free

This is guest post from Mr.Shivlu Jain. He is running a blog related to MPLS VPN

If you have any concerns or any question related with any protocol or networking technology, you can visit his blog and just leave a comment. All you questions will be answered by professionals absolutely free.

Market is on boom and almost every company has opened its door for new positions and everyone is looking for change to grab new positions with new challenges. So make sure that you have prepared the answers for the below questions before your interview. The questions are generic and will make very good impression on interviewer if you answer them in organised and structured manner. The depicted IGP interview questions are for CCNA and CCNP engineers.

1. Difference between RIPv1 and RIPv2?

2. How many number of routes carried by RIP packet?

3. Is OSPF link state or distance vector or path vector protocol?

4. What is the difference between OSPF and IS-IS and which one is preferred?

5. Can we use BGP instead of any IGP?

6. How many network types available in OSPF?

7. Different type of Link State Advertisements aka LSA?

8. LSA 3 and LSA 4 are generated by which router?

9. When to use Stub and Not So Stubby Area?

10. How to get the external routes without making area Not So Stubby?

11. What is the different type of route summarization available in OSPF?

12. What is the requirement of doing summarization?

13. A major network is advertised as summary in one area and few of the routes from that network is configured in another area. What will happen in that case?

14. If any of the OSPF area is not stabilized, does it impact another area?

15. What is the use of forwarding address in LSA 5 and LSA 7?

16. External routes are available in OSPF database but not installing in routing table?

17. If loopback is not configured, what will be the router-id selected by OSPF process?

18. Can we run multiple OSPF process in single router and what is the advantage of using it?

19. What are timers of OSPF?

20. Multicast address of used by OSPF.

21. OSPF works on which layer?

22. What is backbone area in OSPF?

23. Can we use OSPF without backbone area?

24. Is it required that OSPF router-id must reachable in IGP cloud?

25. After configuring new router-id, automatically it will be used or do we need to use some type of command to get it operational.

26. Why the secondary ip address of interface is not advertising in IGP cloud?

27. OSPF neighbourship is not coming up. Please tell the various steps to troubleshoot it.

28. One side MTU is 1500 and another side MTU is 1600. Does it affect neighbourship?

29. Provide process of DR and BDR election.

30. If DR is down and no BDR is configured what will happen?

31. What is the difference between a neighbor and adjacent neighbor?

32. My OSPF neighbourship is showing 2-way, what does it mean?

33. Define different type of OSPF neighbor states?

34. OSPF external routes are not redistributing?

For more CLICK HERE

Route Redistribution Basics: Golden Rules about Route Redistribution

1. Routes can be redistributed from one routing protocol to another. This is the assumption which we are working. But this is not true, routes are not redistributed from one protocol to another. Routes are always taken from RIB not from a routing protocol.

2. The redistributing protocol knows which routes to take from the RIB based on the “known via” information present in "show ip route" details.

3. A route must be installed in the RIB for it to be redistributed in another protocol.

4. Routes redistributed from the routing table are not re-installed again into the RIB.

5. Only the attributes of a route present in the RIB can be used for filtering.

Redistribution Filters:-
1. Redistribution filters can control what information is injected into a routing protocol through redistribution.

2. Filters can also be used to stop routing loops(Read more about layer 3 routing loops) when mutual redistribution between two routing protocols is configured.

Redistribution Filter Tools:-
1. Match metric:- Filtering is possible between all protocols based on metric used.

2. Match Tag:- While mutual redistribution, TAGs can be assigned to routes to stop the routing loop too.

3. Match IP Address:- Matches the prefix, possibly the network mask, depending on the access list type used.

4. Match IP Next Hop Address:- Matches on the next hop listed in the routing table.

5. Match route-type

6. Match Interface

Basics of EIGRP Routing Protocol: EIGRP Cheatsheet – Learn EIGRP in 15 min

Long time folks, was busy with a lot of projects. Hope coming year gets less busier and I get to get my hands more dirty on networks and network security. In the meantime, here is an EIGRP cheat sheet which I thought will be helpful to folks who just want a quick theory review of Cisco’s EIGRP. Though I wanted to cover a lot more in cheat sheet like EIGRP technologies, planning but it would have defeated the purpose of cheatsheet. Never mind, I am preparing a more comprehensive EIGRP guide which I might publish soon depending on the feedback received. In the meantime, You can find the cheatsheet at Slideshare and Scribd.

Eigrp Cheatsheet - EIGRP in 15 min - Rishabh Dangwal - www.theprohack.com from Rishabh Dangwal

Source: PROHACK

About the author : Rishabh Dangwal

Rishabh Dangwal is a no-nonsense network geek who has got a thing for guitars, retro games and emulators. When he is not tinkering with devices and gadgets, he can be found reading novels by Fredrick Forsyth. Follow him on Twitter

Delhi RedFort True Story & True History: Social Engineering Attack Example

What is social engineering...to manipulate others mind. Here is the one example of social engineering attack.

Attackers are always looking for new ways to access information. They will ensure that they know the perimeter and the people on the perimeter - security guards, receptionists and help desk workers - to exploit human oversight. People have been conditioned not to be overtly suspicious that, they associate certain behavior and appearance to known entities. For instance, on seeing a man dressed in brown and stacking a whole bunch of boxes in a cart, people will hold the door open because they think it is the delivery man. Here in this example you can easily see that how few guys has manipulated the entire history.

After reading this, you are open to make your own decision. I have posted the facts available.

READ FULL POST HERE

History of Taj Mahal: The True Story | Best Social Engineering Attack Example

Friends, few days back I have posted an interesting post on my VENTUROUS BIKERS blog. Suddenly I realized that if all the facts photographs are real, which I received from one of my resource, it could become the BEST EVER & BIGGEST SOCIAL ENGINEERING EXAMPLE IN HISTORY.

I like to share that post with you also. After reading this, you are open to make your own decision. I have posted the facts available.

Except Prof. Oak. no one has ever challenged the statement that ........

"Taj Mahal was built by Shah Jahan"

BBC Says ...........

Taj ...........

A hidden truth ..........

Never say that .........

It's a Tomb ..........

READ FULL STORY HERE

Take the Hackers Quiz

Many computer hackers have broken the law in their careers, but some actually go on to have productive roles in the computer industry. And while hacking is certainly a crime, these cases are always complex. Try our ultimate hacker quiz.

START QUIZ

Google Search is only 18% Search: Is Google becoming a Yahoo?

I was recently testing some of the keywords and positions for our help-desk app and it suddenly occurred to me that 80% of the page were not actually the search results. Check this out:

My brain got used to filtering the ads out, so it never popped into my head before... We are used to this picture. I actually had to get up from my laptop, grab a coffee and then glance back at my monitor from across the room to notice this.

ADs vs Results: area size

Now, we're all technical people so let's do the math:

• The screenshot above is 1280x960 pixels (a typical resolution for a 13" wide-screen laptop and some older 15"s). My Mac has a 1920x1200 resolution, but still I prefer not to browse in full screen (actually, the only apps I run full-screen are the development ones - Sublime Text, Visual Studio, XCode etc.).
• The search results take up 535x425 pixels.
• Which makes it 18.5% of the window

I do understand that this stuff is resolution-dependent, but still... Only 18.5% of the screen is devoted to something that people are actually looking for.

Let me show you what "18.5% of the screen" really looks like:

ADs vs Results: UI elements count

Now, enough with the area size. Let's count the links - the clickable text UI elements.

The page has about 45 different links in total. Only 5 of them are the actual search results (I do not count the "sitelinks" - the sub-links shown under some results and ADs). Which makes it about 11%. Only 11% of the total links on the page are the actual search results.

(If we do include the "sitelinks", it makes 57 links, 10 of which are the results, which is 17.6%).

OK, let's be fair, some of the links are the tools ("Google Docs", "Gmail"), some are search modifiers ("Search near...", "Search images"), some are Google-Account utilities ("Sign in", "Settings") so let's drop these links and buttons... Let's count only the "blue stuff". I.e. links that "look like" the search results, not including the "sitelinks". We have 18 links in total. 5 are the results. Which is 27%.

The bottom-line is: even dropping all the "secondary" UI-elements, the Ad/Results ratio is almost 4-to-1.

Was it always like this?

Unfortunately, I was unable to find a screenshot of Google's result page back from the late 90s, but found some stuff from the 2000s. I did an image search for "large" images, dated "before 2008", searching for "google results", "serp page" etc. Obviously, I was not able to find a screenshot for these particular keywords ("saas help desk"), so I tried to find a screen with as many ads as possible. Since "saas help desk" turns out to be a pretty competitive term. Here's what I found.

The AD/Results ratio is 8 links to 7. Which is 47% of the links are the actual results.

Now, the area. The results are 779x595 pixels. The total size is 1108x790 (which is even smaller than my original screenshot). Which makes it 53% of the screen is taken by the results, more than a half (actually, even more, since it's a smaller screenshot and there are no more ADs below the fold).

What does this mean?

Google has cut down the results area by three times - from 53% to 18%. The company is obviously interested in people clicking more ADs (in fact, I believe that's also the true reason behind "Penguin" and "Panda") since it's the company's primary source of income...

But all I know is that in the early 2000s Google has become the #1 search engine because of the three things:

1. Relevant results
2. The speed at which they were served
3. The simplicity of the UI

Looks like they're dropping #3 now. Is Google becoming a Yahoo?

SOURCE: http://blog.jitbit.com

Join Indian Cyber Army | Hackers VS Cyber Weapon

Can Internet be Used as Weapon

To know HOW TO JOIN INDIAN CYBER ARMY? Read Below

Yesterday I was thinking about terrorism. The most dangerous weapon currently we have is in the form of chemical weapons, nuclear weapons or biological weapons. If any terrorist group get access to any of such weapon, he can destroy the complete infrastructure of a city, state OR even a country. So many controls & security measures has been taken by government so that all such weapons will be out of the reach from terrorists.

But we all are living in new era now. We all are part of a new world, directly or indirectly, which we might not aware of & that is INTERNET. Yes..It’s a virtual world which becomes necessity for everybody these days.

Currently we have no control on the cyber space. Anyone with a little knowledge of computers can enter into this virtual world and do such thing which no one can even imagine. On this virtual world, age doesn’t matter, whether you are 10 years kid or 70 year old, Internet is providing equal level of power to all. Only matter is how perfectly you are using it. Let me take a small live example. Suppose if I just Google the term - how to make a bomb all methods and video will be available. So any one can put few more efforts and innovation to make own BOMB.

This Google search is the simplest example. Here the major concern is WEAPON WITH MIND. Just think, till date all the available weapons we have has no mind. Such weapons cannot upgrade themselves with technology. As technology changes weapon changes. One day every weapon is replaced by some other better weapon. This is only because such weapons have no mind to think and no mechanism to upgrade. But now days, we have weapons OR better to say underground weapons which can use their MIND to upgrade their skill set as per latest technologies. All such Cyber Weapons are known as HACKERS. YES HACKERS can be used as CYBER WEAPONS and all such cyber weapons will play the major role during the next world war.

Everyone including military leaders has realized that most of the next world war will be fought on the cyber space and only those will win, who have the best experts knows as HACEKSR or as I termed then as CYBER WEAPON. This Cyber War will be the most destructive war & can destroy the infrastructure of any country in less than a minute. The latest example is STUXNET. Stuxnet was the targeted cyber attack aimed at destroying an industrial process in the physical world & it was invented specifically to target part of the Iranian nuclear infrastructure.

In India, still we are lacking in this front and no have come forwarded to raise his voice against this issue. Is this lack of government attention OR lack of military leaders?

For a moment if I consider that government & military leaders have no more idea in this cyber field, but what about our ETHICAL HACKERS of India? Have they ever thought about this issue or not? Whether it’s a CEH institute or an individual one, almost everyone is doing the same thing that is WORKSHOPS, WORKSHOPS & MORE WORKSHOPS. Till date I have not seen any of the ETHICAL HACKER, who has raised his voice for country.

HACKING is an ART. HACKING MEANS INNOVATION. Somewhere this ART has been replaced by few outdated tips & tricks. Just think why the term HACK creates so much hype in young generation. It’s only because they have no proper and valid resource to learn this. HACKING is also a subject just like MATHS, ENGLISH, ELECTRONICS & MECHNICAL.

It’s my appeal to government authorities that include HACKING as a subject in the course of students.

If we make valid the subject HACKING in school & colleges in a well formatted course, it would be the revolutionary step in the field of cyber security in India. Here most of the guys can ask me that there are so many institutes running hacking classes. Well no doubt, I am saying that include CYBER ETHICS & CYBER Security as a subject in the school, so that from the grass root, students can learn about cyber respect and behave well online. Once they enter into college, we can make ETHICAL HACKING subject as an optional subject. Let me take an example of BTECH & engineering students. There are so many subjects which are optional, from which students have to choose according to their interest. In the similar way we can also offer ETHICAL HACKING as an optional subject so that interested students can choose this field as a career.

Few days back while surfing Internet, I found a similar term know as "Information Weapon". Professionals has started thinking about this Information Weapon OR Cyber Weapon & I doubt that In India any one from government higher authorities OR military leaders taking this issue seriously. No one is realizing this truth that misuse of cyber can turn into serious issue any time. The major part of any country’s Infrastructure will directly be affected due to cyber attack including financial systems & Telecommunication systems.

A simple hacking of Vijay Mallya becomes national news. Just think that how website defacement attracts everyone. Well let me clear one point here that such website defacements are not CYBER WAR. It’s only the EGO war between technical guys of two countries. Just imagine how such script kiddies attract everyone. Now just think that what would be the impact when actual cyber war starts. The truth is all those guys are not real hackers. They all are script kiddies. In hacking world they all are knows as N00Bs. I am saying only because website defacement is not required any specialized skill or new development. If you know little bit of SQL injection then you can bypass the authentication and get the access to ADMIN panel of the website. After that you have to upload the SHELL and boooom…. All done..just few clicks on you uploaded shell and website defaced. If you are little technical and have little more in depth knowledge, you can do server rooting in which you will get the root access to the server. Once the server get rooted, you have all the websites in your hands hosting on that particular server. So this is what exactly hackers are doing. In this the most important thing is SHELL. And the REAL hacker is the person who has developed that SHELL. Few freely available shells are C99 shell, C100 shell, ex0shell, GNY shell, rootshell, megabros, cpanel & R57 shell.

In my personal opinion, the real hacker is one who can develop his own SHELL and can create his own exploits. Using existing exploits & others developer’s shells, any TOM, DICK & HARRY can use it and can claim himself as a HACKER, which is not true.

For cyber peace in India I am happy to be part of a revolution in Indian Cyber History. A new young army for Cyber security of our country INDIA.....INDIAN CYBER ARMY. This army will not hack or crack any country's server, but secure the Indian cyber Infrastructure & protect the Indian cyber space from any cyber attack. Will you join this Cyber Army & wanna be part of it ?? Come & Join Guys.

HOW TO JOIN INDIAN CYBER ARMY?

Well on internet you will see a lot of so called cyber armies claiming to be cyber army of India. Asking you for paid seminars & bah blah blah.....

Be-aware of any such group or army. The best is to enhance you knowledge in the field security. Try to learn security...not HACKING. You will be fooled by name of hacking. Hacking & security are different sides of same coin. Till date no hacking cert is well recognized in INDIA and there is no value in any organization. All such stuff is bullshit.

In my personal opinion, If you learn your self, share your knowledge & best if you are getting paid for it, CONGO..YOU ARE ONE OF FROM INDIAN CYBER ARMY. Here I am mentioning the certification which are very well recognized in world wide organization. All these certs are related to SECURITY and also help to get you placed in organizations.

1. CCNA (Cisco Certified Network Associates)
2. After CCNA, you can go for CCSP (Cisco Certifies Security Professional) - Help you to get into network security
3. If you are interested in LINUX, go for Red Hat Certified Security Specialist (RHCSS)
4. The best is ISO 27001 lead auditor at you initial level. If you do this, you will be certified s a auditor for all security related audits includes in ISO 27001. It is a professional certification for auditors specializing in information security management systems.

At your initial stage, this is enough to get start in a correct direction. Still any query, feel free to ask.

---Do you want to share you views?? Just leave a comment here. you can also drop an email on mail@amarjit.info

Exclusive Interview of Rahul Tyagi: Author of “Hacking Crux 2

Exclusive Interview of Rahul Tyagi: Author of “Hacking Crux 2 

Source: Softpedia 

Rahul Tyagi, a respected ethical hacker from India, is about to release his latest work, a book called “Hacking Crux 2.” This is meant as a guide to anyone who wants to learn about hacking and defending themselves and others against cybercriminal plots. 

Because the book looks very promising, we have decided to interview the author to find out more about his work and his new creation. Besides discussing his contributions to the IT security industry, Tyagi also shared his insight regarding the fact that many Indian ethical hackers are called fakes. 

Softpedia: Please introduce yourself for our readers.

Rahul Tyagi: My name is Rahul Tyagi and I am 24 years old. I am a person for whom work is more important than anything in the world. I was born in a middle class family in Gurdaspur, a small city in Punjab. My father is an accountant and my mother is a housewife. I love to interact with new people and share knowledge.

At the age of 17 my father brought the first PC to my home for his accounting work. I remember spending hours on my father's computer, getting in trouble for messing things up. It occurred to me that the only way you really learn about something is by breaking it, then fixing it. 

I am Lapi-Worm kinda person who works 24/7 on a laptop for many days without sleep. My mind always thinks of something, my mind never stays free. Because one thing I learnt in my life: a free mind is the house of Ghost. I admire Steve Jobs and I want to contribute to the cyber society just like him. 

Softpedia: What qualifies you as an ethical hacker? Tell us about your previous experience and studies.

Rahul Tyagi: Well, first I will try to explain the meaning and responsibility of an ethical hacker. According to me, an ethical hacker is a computer geek, who obviously thinks more out of the box than other computer lovers. The main responsibility of an ethical hacker is to protect people from the cyber space attacks. 

Protection can be at corporate level by securing their servers, by patching the web vulnerabilities or maybe securing a common man’s Gmail account by adding two-step verification on his/her account. 

I think I have trained more than 10,000 people from all around the world physically and online in the last 7 years, and today if they are using their computers and internet freely without any problems then I think my work is done. 

I did my pre schooling from my hometown. I have obtained a bachelor’s degree in Computer Applications at the Punjab Technical University. After my three year graduation I got admitted to India’s largest university, the Lovely Professional University (LPU) for my masters, i.e, Master in Computer Applications (MCA), and that was my life’s best decision. 

At LPU I learned a lot because there I found the best infrastructure required for penetration testing. I hacked into LPU’s University Management System twice and found much vulnerability in the network, but instead of doing harm I reported the vulnerability to the authorities there. 

In my 5th semester of masters I got placed in TCIL-IT Chandigarh as their brand ambassador and that was something big for me. Later I was selected as Vice-President of Cyber Security and Anti-Hacking Org India. Last, but not least, I am working as the Technical Head at the News Paper Association of India. 

For the past two years I have been associated with DEF CON India meets and I was one of the leading speakers in DEF CON Chennai, where I presented my paper named “Busting Windows in Backtrack 5” and DEF CON Rajasthan, where I presented my paper called “The Endless Fight with Global Cyber Crime”. 

This month you can see my article in one of the reputable security magazines named Pen Test. 

Softpedia: Tell us a little bit about your new book “Hacking Crux 2”. What IT security topics does it cover?

Rahul Tyagi: Hacking Crux 2 is a book which is like a mirror of me. Everything that I learned in the past I’ve put into this book. I had many issues with the content of the book, but after 8 months of “blood burn effort” from my part and my publisher, Mr. Dev, I am happy to present Hacking Crux 2. 

Initially I wanted to publish it in January, but after that I decided to make it more knowledgeable and I tried to cover every aspect related to computer security in it. We tried to make this a lively book, having 90% screenshots for the readers so that it will be easy for them to implement testing by just watching the pictures, rather than reading theory.

Here are the chapters of the book:

1. Introduction to Ethical Hacking
2. Information Gathering
3. Advance Google Hacking
4. Trojan and Backdoors
5. Binder and Crypters
6. Website Hacking Techniques 
7. Spamming Techniques
8. Email Hacking and Countermeasures 
9. Advance System Hacking 
10. Steganography Terrorist’s Way
11. Basics of Python for Coders
12. Virus and Worms
13. Proxy Servers ad VPN
14. Exploit Launching with Perl
15. Advance Mobile Hacking 
16. Wireless Attacks
17. Penetration Testing With Backtrack 5 R1 

We have a total of 17 chapters covering every possible ethical hacking module. The main highlighted topics of the book are Binder and Crypters, Advance System Hacking, Email Hacking and Countermeasures, Exploit Launching in Perl, Advance Mobile Hacking , Penetration Testing With Backtrack 5, and, last but not least, my favorite, Basics of Python. 

This is the first book on ethical hacking ever published in India having so many chapters at such a small price, i.e. INR150 , under 5 USD. 

I tried to make this book as informative as possible so that after reading this book no one will need to join any expensive ethical hacking courses. If you believe my words, then Hacking Crux 2 contains all you ever need and wish to know about the so-called “Ethical Hacking”. 

Softpedia: When will the book be released and where will it be available?

Rahul Tyagi: We are trying to publish it worldwide through eBay, Amazon, Flipkart, Snapdeal to our international readers before May 15. Indian readers can get this book from any nearby bookstore starting with the last week of May or the first week of June. Also, online purchasing options like Flipkart and Snapdeal will be available. 

And if someone is facing any problems then they can send an order to hackingcrux2@gmail.com. 

Softpedia: In the past period many Indian ethical hackers have been named fakes and mere marketing stunts. On the other hand, we have white hats, such as Himanshu Sharma, who try to wash away this stained reputation gained by many Indian security experts. What makes you different from the fakes? What do you hope to achieve with this book and with your work?

Rahul Tyagi: If you talk about Himanshu, then yes, he is like my younger brother. Even though he is younger than me, I still respect his talent from the bottom of my heart. 

Now, let’s talk about some fake hackers. According to me, there are some reasons why people call some Indian ethical hackers fake.

The first reason is that many ethical hackers claim to be great in their work, but if you talk about statistics, then they are ZERO. You can take a look at attrition.org. 

They exposed many ethical hackers who were just fooling people with ethical hacking courses, but in reality the things they teach are just internet filtering techniques and tricks, which, from my point of view, are not going to help any person get a reputed job in any company. 

That’s why those who have done the ethical hacking certification from these kinds of hackers later abuse them and say that they were fake hackers, who cheated them.

The second reason is that people from the cyber world these days are becoming smarter day by day. They are bored with traditional hacking tricks, hacking websites with SQL Injection, NETBUS, Proxy servers and other “noobish” things, which today anyone can do even at the age of 10. So if you are repeating the same and same thing from 2000 to 2012, then obviously you deserve the tag of fake hacker.

As far as I am concerned, it’s not that I don’t have critics, but today almost all white hat and black hat communities know me, respect me and motivate me. I have many friends from both black and white hat communities who from time to time help me upgrade myself. 

This is why I was the first white hat ethical hacking trainer who spoke at DEF CON meets in India. My paper is there in Exploit-DB and Packetstorm Security and if you compare this fact with the ethical hackers tagged as fakes, they don’t submit any papers and they never dare to enter into conferences like DEF CON and NULLCON.

The only thing that makes me different from other ethical hackers is that I do not forget my past, from where I rose. Even though I have 38k followers on Twitter and 5k friends on Facebook , I reply to every possible query they ask me. 

I also believe in contributing with new stuff to cyber space, hence a few months back, I released a full Python language-learning course on YouTube and it was the first ever basic Python video lectures series made by an Indian ethical hacker. 

With all this I don’t think anyone can say I am a fake hacker. If anyone wants to say that, I ask him/her to compare my contribution with the ones of other fake ethical hackers and, they will get their answer automatically.

Finally, I hope my new book Hacking Crux 2 will help you to learn all the hidden areas of ethical hacking, especially ones that are never revealed by any ethical hacker, ever. I promise that if you trust me and buy this book you will thank me for sure.

You can contact me on: Facebook, Twitter or by e-mail. 

How LSA Works with/without OSPF AREA 0 | Running OSPF without AREA 0 By Anuj Tyagi: Case Study

Hi Friends, I have received a complete case study done by Mr.Anuj Tyagi on OSPF routing protocol. After reading our article Configure OSPF without AREA 0: CCNP OSPF Case Study, he also tested the similar scenario in his testing LAB. I am publishing his case study as it is without any editing so that guys who are learning networking & OSPF, will get some benefit from this.

Running OSPF without AREA 0

Topology 1: Connecting OSPF Area 2 and area 3 without using ABR.

Interface configurations are mentioned above in the topology.

Remember,

· ABR: ABR is a area border router that contain interfaces in atleast two separate area out of which one should always be in AREA 0.

So, surely above topology don’t have any ABR and we will be going to test how routers behavior in absence of backbone area.

After configuring OSPF routes on R1, R2, R3 as in above topology, we analysis all Routers neighbor table .

That shows Full Neighborship Status for neighbors . Take a look again at the neighbor table,

Neighborship is being maintained with it’s directly connected interfaces.

Now, if we will try to PING

· R2 S0/1 , surely we will get successful reply .

· R2 S0/0, we will get successful reply (as it is directly connected)

· R3 S0/0, obviously we R1 can’t reach 2.2.2.1 of R2 we will be unable to get reply from R3 s0/0.

Why? Just take a look at the neighborship table of R1 again .

So, what is happening behind the scenes when R1 trying to communicate with 2.2.2.0/24 network .

R1 can’t even find the path or from which interface R1 should send the packets .

Now lets take a look at the Router OSPF LSA’s,

· R1 having LSA1 (router-id) updates of only those routers in same area.

Reason : There is no ABR to send LSA3 (summary LSA) updates . ( remember ABR? )

After looking at LSA and neighbor-table, you can guess about the routes will be there in Routing Table.

Again, they are also from directly connected interfaces with Routers.

Now make it a bit interesting, we will going to add interfaces on R2 in Area 0 .

Now, compare neighborship table of Router R1,R2,R2 with and without AREA 0 (backbone area) .

R1 topology table with AREA 0

We can now clearly see LSA3 in the table, apart from networks of Area 0 R1 got one more network advertisement in LSA for 192.168.2.0/24 and 2.2.2.0/24 in summary LSA updates from R2(ABR router).

While in

R2 topology table without AREA 0

In the same way, AREA 0 will also make Router R2 as ABR now and that will add a lot to topology table of Router R2 .

Now, it is behaving like ABR as it is acting as both in AREA-2 and AREA-3 completely.

Router R3 also getting LSA1 and LSA3 updates from R2(ABR).

Note: LSA2 updates (network LSA) are only advertised in Non-broadcast where DR & BDR exist.

Now , also PING will be successful from any Router to any network in topology.

Conclusion:

OSPF will not form neighborship with inter-area(IA) routes if there is no backbone area exist or we do not use ABR . In other words, Each area share it’s link state database only through AREA0 to any other AREA. It will make neighborship only with directly connected networks

LSA 1,2 do not need Area0 to share it’s Acknowledgement but LSA2 will form only in non-broacast network (like frame-relay) where DR will be having responsibility to send updates but we must need to have AREA0 to send LSA 3, 4, 5 & 7 updates.

----------------------------------------------------------------------------

R1 Config

Using 1024 out of 57336 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R1
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
memory-size iomem 5
ip cef
!
!
ip auth-proxy max-nodata-conns 3
ip admission max-nodata-conns 3
!
multilink bundle-name authenticated
!
!
archive
log config
hidekeys
!
!
!
interface FastEthernet0/0
ip address 192.168.1.1 255.255.255.0
duplex auto
speed auto
!
interface Serial0/0
ip address 1.1.1.1 255.255.255.0
clock rate 2000000
!
interface FastEthernet0/1
no ip address
shutdown
duplex auto
speed auto
!
interface Serial0/1
no ip address
shutdown
clock rate 2000000
!
router ospf 100
router-id 1.1.1.1
log-adjacency-changes
network 1.1.1.0 0.0.0.255 area 2
network 192.168.1.0 0.0.0.255 area 2
!
ip forward-protocol nd
!
!
ip http server
no ip http secure-server
!
!
line con 0
line aux 0
line vty 0 4
!
!
end

-------------------------------------------------------------

R2-ABR Config

R2-ABR#show configuration
Using 1114 out of 57336 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R2
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
memory-size iomem 5
ip cef
!
ip auth-proxy max-nodata-conns 3
ip admission max-nodata-conns 3
!
multilink bundle-name authenticated
!
!
archive
log config
hidekeys
!
!
interface FastEthernet0/0
ip address 172.16.1.1 255.255.0.0
duplex auto
speed auto
!
interface Serial0/0
ip address 1.1.1.2 255.255.255.0
clock rate 2000000
!
interface FastEthernet0/1
ip address 172.17.1.1 255.255.0.0
duplex auto
speed auto
!
interface Serial0/1
ip address 2.2.2.1 255.255.255.0
clock rate 2000000
!
router ospf 100
router-id 2.2.2.2
log-adjacency-changes
network 1.1.1.0 0.0.0.255 area 2
network 2.2.2.0 0.0.0.255 area 3
network 172.16.0.0 0.0.255.255 area 0
network 172.17.0.0 0.0.255.255 area 0
!
ip forward-protocol nd
!
!
ip http server
no ip http secure-server
!
!
control-plane
!
!
line con 0
line aux 0
line vty 0 4
!
!
end

-------------------------------------------------------------------------

R3 Config

Using 1024 out of 57336 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R3
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
memory-size iomem 5
ip cef
!
!
ip auth-proxy max-nodata-conns 3
ip admission max-nodata-conns 3
!
multilink bundle-name authenticated
!
!
!
!
archive
log config
hidekeys
!
!
!
interface FastEthernet0/0
ip address 192.168.2.1 255.255.255.0
duplex auto
speed auto
!
interface Serial0/0
ip address 2.2.2.2 255.255.255.0
clock rate 2000000
!
interface FastEthernet0/1
no ip address
shutdown
duplex auto
speed auto
!
interface Serial0/1
no ip address
shutdown
clock rate 2000000
!
router ospf 100
router-id 3.3.3.3
log-adjacency-changes
network 2.2.2.0 0.0.0.255 area 3
network 192.168.2.0 0.0.0.255 area 3
!
ip forward-protocol nd
!
!
ip http server
no ip http secure-server
!
control-plane
!
!
!
line con 0
line aux 0
line vty 0 4
!
!
end