Exam 300-410 topic 1 question 49 discussion

So in this case we are going to set the local preference inbound and outbound the as-prepend so answer is C!

LP will correct outgoing traffic. What will happen to the incoming?

That is not really true, with that you will only be influencing the outbound traffic, what about the inbound?

It´s making R1 think that incoming and outcoming traffic from link A is taking an extra hop, therefor making the as-path longer for R2, reference to this links "We will now use a technique called AS path prepending, which consists of adding extra “fake” hops to a path using our ASN multiple times." https://nsrc.org/workshops/2018/ubuntunet-nren-bgp/networking/nren/en/labs/bgp-policy-as-prepend.html#:~:text=We%20will%20now%20use%20a%20technique%20called%20AS%20path%20prepending%2C%20which%20consists%20of%20adding%20extra%20%E2%80%9Cfake%E2%80%9D%20hops%20to%20a%20path%20using%20our%20ASN%20multiple%20times. and https://www.ccexpert.us/routing-switching/step-4-shortest-aspath.html#:~:text=The%20concept%20and,not%20be%20intended. You can check a configuration example here https://community.cisco.com/t5/networking-blogs/bgp-as-path-prepending-configuration/ba-p/3819334

That is correct. Config makes Traffic take link B while A is under maintenance. route-map link-a-in permit 10 --> Allow incoming routes from A route-map link-a-out permit 10 --> Prepend own AS-PATH so that AS-PATH becomes longer (for R2) to influence inbound traffic. route-map link-b-in permit 10 set local-preference 200 --> Set local pref for routes coming in from B. Default local pref is 100 so R1 will choose B over A. route-map link-b-out permit 10 --> permit all routes advertised to B. Hope this clears. Please comment any mistakes/corrections.