Exam 350-501 topic 1 question 45 discussion

we apply local-pref to inbound routes to affect outbound traffic

I REALLY think the answer is B. I may be reading to much into this, but here's my take. This is the Service Provider exam, so in my opinion we need to approach this as being the service provider, and therefore, need to see this as changes that need to be made on our equipment. Service providers generally don't make changes of this kind for one customer but they do have BGP policy lists that are available to customers to use to put community tags on their prefixes that will cause policies on the service provider to be enacted. Through the use of community tags by the customer, and community lists by us (the service provider), the path can be manipulated by use of a route-map that adjusts the local preference of how to reach the customer's site. So I think B is the best answer.

I agree it should be D considering we must interpret this question from the ISP point of view. We, on the ISP side, would be configuring a local preference on the inbound routes from the customer AS to prefer one path over the other.

The interested traffic to influence here is the one we are forwarding OUT to other BGP speakes (BGP peers). Option B then.

Could the question be worse worded? here cisco is evaluating whether you have understood the question rather than the content of the question itself, which is what the exam should focus on

Higher local preference on routes INBOUND makes them preferred OUTBOUND

D - you have to make the local-pref HIGHER for routes coming INTO the AS to make the AS prefer that exit point

I'd go with A simply because this is from a service provider angle, you can only influence metrics towards the customer to effect his outbound traffic towards you, not local pref

The question is not copied correctly. it should be Which BGP attribute should be configured to choose specific BGP speakers as preferred exit points for the customer AS?

It is not stated that customer asks ISP for support. Outbound refers to the outbound traffic, not BGP advertisements. Local preference applies in the incoming routes, influencing outbound traffic. https://community.cisco.com/t5/other-network-architecture/bgp-inbound-and-outbound-traffic/td-p/337728 Answer is B

It's pretty clear the configuration is on the customer side (it is mentioned 'the customer asks ISP for support'). Why would an ISP even care on which link it sends traffic to a customer? If a multihomed customer wants one link to be preferred over the other for incoming traffic, he will configure the policy, not the ISP. But in this case, the question is about outgoing traffic, so the answer is D.

It's pretty clear the configuration is on the customer side (it is mentioned 'the customer asks ISP for support'). Why would an ISP even care on which link it sends traffic to a customer? If a multihomed customer wants one link to be preferred over the other for incoming traffic, he will configure the policy, not the ISP. But in this case, the question is about outgoing traffic, so the answer is D.

Ok, not sure how many of you have worked for an ISP before but I have. The question is based on you helping your customer. So the configuration will be what they are doing in their network which throws MED out of the equation since that's something the ISP would do to influence their traffic outbound. Local Pref is the way you influence how you route outbound for the entire AS domain. However, the policy is applied to the routes you learn which means as the route comes INBOUND you use a matching clause and set the local pref. The correct answer is Local Pref inbound FOR THE CUSTOMER, which is who you are helping.

I think in the end it depends if its iBGP or eBGP. if it is eBGP then the answer is A but if its iBGP then the answer is B theres not enough information here. Customer gets a IP from the ISP, so the ISP to the client is iBGP because its internal to the AS. It would be different if the guest had two ISP connections, or the ISP had to go through another external route to reach the customer, I dont think that Cisco made it this complicated, I have to go with B since its more simple. Again its iBGP versus eBGP there's not enough information therefore I go with simplicity.

answer must be A : Read the question carefully: A customer of an ISP (assume AS1)/.....and at last preferred points for the customer AS.....there are 2 separate AS, so MED will come in picture.....thus A will be ans

its none of the above guys, you're all wrong

Also, MED do not fit the description. The default behaviour of MED is to only compare if the AS is the same for the path. One would expect an multihoming scenario being in the question then. And MED is also 6 in path selection. Highest local pref to inbound is the answer.