Refer to the exhibit. A network engineer for AS64512 must remove the inbound and outbound traffic from link A during maintenance without closing the BGP session so that there is still a backup link over link A toward the ASN.
Which BGP configuration on R1 accomplishes this goal?
A.
B.
C.
D.
The correct configuration to accomplish the goal of removing inbound and outbound traffic from link A during maintenance without closing the BGP session is to use a combination of AS path prepending for outgoing traffic and setting the local preference for incoming traffic. The correct option is C. This configuration will make sure that the BGP session remains active while preferring link B over link A by setting a higher local preference for link B (200) and using AS path prepending for link A to make it less preferred for incoming traffic. This ensures that the traffic will prefer link B for both inbound and outbound directions during the maintenance of link A.
Hello, the only one correct here is C because the other one are making the incoming routes from R2 to be better than the routes of router R3. In this case cause we have only one router we can put the weight 100 inbound for the updates coming from R3 (via a route-map that is going to set the weight to 100, by def is 0), then we configure AS prepend in R1 in outgoing direction for force R2 to go via R3 for reach R1 because the router see two organization instead of one to traverse.
So in this case we are going to set the local preference inbound and outbound the as-prepend so answer is C!
the option corret is C
none of them is correct you do not need all these fancy route-map links to meet the solution only route-map we need is route-map link-b to increase LP. that is all create access-list create route-map match ip add set the LP apply the route-map to link b BGP
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?
THe given answer is correct LP default is 100. Highest wins.
C is correct
The given answer is correct "C"
Yes correct
Can someone kindly explain what this is doing? Is this making the traffic start to take Link B while traffic A undergoes maintenance? Also, what is the purpose of "set as-path prepend 64512" for link A? Isn't local preference enough? Please more input is appreciated.
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.
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
The given answer is correct