CCIP questions

Unanswered Question
Jul 5th, 2007

What is the main raison for a multihomed costumer to apply outbound route filter to filter the BGP update from customer router to a service provider router ?

A. To ensure that the return traffic in the customer network 'll be load balanced between the service providers.

B. To ensure that the outbound traffic from the customer network 'll be load balanced between different service providers.

C. To prevent the customer network from becoming transit AS

D. To allow the customer network from becoming transit AS

E. To reduce the size of BGP table on the customer network internal (core) routers.

F. To reduce the size of BGP table on the customer network internal (core) routers.

I choose answer E) as the best answer, what do you think about it ?

Best regards.

I have this problem too.
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mohammedmahmoud Thu, 07/05/2007 - 01:53

Hi,

If this question was about ORF, then i think that there is a typo, the answer should be "To reduce the size of BGP table on the customer network edge routers running BGP with the provider".

But if its around configuring ordinary out route filters from the customer to the provider then the answer should be "To prevent the customer network from becoming transit AS", which is IMHO the goal of the question, as it is talking about a multihomed customer.

HTH,

Mohammed Mahmoud.

ms01 Thu, 07/05/2007 - 04:22

Its C.

With outgoing route-maps your are able to control your received traffic.the resultant is, that a normal multihomed customer dont want to be a transit "ISP", and filter out all bgp routes except his own bgp networks.

regards

Michael

Paolo Bevilacqua Thu, 07/05/2007 - 03:52

I think it would be A and D. E / F (same answer ?!) are not applicable because the question is about _outbound_ filtering.

Hope this helps, please rate post if it does

mohammedmahmoud Thu, 07/05/2007 - 04:05

Hi Paolo,

I think that multihomed customers need to do outbound filtering, in order to filter the received routes from one of the ISPs before sending any routes out to the other ISPs in order to prevent itself from being a transit AS.

BR,

Mohammed Mahmoud.

Paolo Bevilacqua Thu, 07/05/2007 - 04:33

EDIT: BIG DYSLEXICAL TYPO ON MY SIDE, I SAID D WHILE MEANT C :)

Yes, we be both "meant" to say one correct answer is "C".

But, the typical approach in cisco tests is to trick (and potentially fail) you on multiple answers questions, on which you have to give _all_ the correct answers in order to score.

Now, I think that also "A" is correct, because if I filter (some of) my own prefixes across multiple ISPs, I will achieve some sort of load balancing on "return traffic".

I've been burned too many times by this kind of multiple answers questions, and hope someone can confirm the above ...

mohammedmahmoud Thu, 07/05/2007 - 04:51

Hi Paolo,

I totally agree with you about the tricking stuff in Cisco exams (i've fallen in some tricks before:) ), but the statement "To ensure that the return traffic in the customer network 'll be load balanced between the service providers" seems incorrect ,it would be some kind accepted if it was load sharing traffic between the providers not absolute load balancing the traffic, plus in the exam if there can be multiple answers it is stated.

BR,

Mohammed Mahmoud.

Paolo Bevilacqua Thu, 07/05/2007 - 05:04

Mohammed, this is the very point.

You go to the test and encounter questions incorrectly or ambiguously formulated, and not just by one person opinion, but by many professionals. You have no remedy, and if these accumulate enough, they will fail you.

Even worst when the exam is in beta because is "newly formulated" and has, by same cisco's admission bugs that are corrected later !!

How can they allow having bugs in tests where money, time, career and pride are at stake!!

stephtchoko Tue, 07/10/2007 - 01:44

Sorry about the last answer, it is:

F. To reduce the size of BGP table on the service provider internal (core) routers.

Regards.

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