Refer to the exhibit. An engineer configured BGP and wants to select the path from 10.77.255.57 as the best path instead of current best path. Which action resolves the issue?
Refer to the exhibit. An engineer configured BGP and wants to select the path from 10.77.255.57 as the best path instead of current best path. Which action resolves the issue?
The goal is to make the path from 10.77.255.57 the best path. Since the current best path is from 10.57.255.11 and the AS_PATH for this route is shorter than for 10.77.255.57, we need to make the current best path less preferred. This can be achieved by using AS_PATH prepend on the current best path. Adding additional AS numbers to the AS_PATH of the current best path will make it less preferred, allowing the path from 10.77.255.57 to be selected as the best path.
Output shows #9 different possible paths. local routers has chosen #6 as best-path. it is asked to what is needed to make path #5 the best-path. - A - wrong (lower MED is preferred.) - B - correct (by adding extra AS_PATH makes the current best-path #6 less preferred compared to route #5) - C - wrong (this is the opposite of B) - D - wrong (higher LOCAL_PREF is preferred not lower!)
Wondering how to guarantee the #5 path will be chosen as the alternative best rather than any other paths if prepending #6 path as the current best? thanks!
My assumption is that the best path is chosen for the lowest BGP router-id, the lowest is 10.57.255.11 and the second lowest is 10.77.255.57. If we make 10.57.255.11 less preferred by AS Path Prepending, 10.77.255.57 is going to be selected as best. All other attributes are the same.
Although B is sort of making sense and according to commen sense, it still hard to convince answer B is correct due to there's other BGP routes with less AS path and the same other attributes. e.g. metric, localpref but not be choosen the best. E.g. 172.16.254.234. it's a tricky question.
B is correct
D is correct i think Explanation From the output, we learn that the current best path is from 10.57.255.11 (which includes “…valid, confed-external, best“) and this path is 2 ASes away (64955 65003). Although there are some paths with only 1 AS away (path from 172.16.254.234 for example) but they were not chosen the best path so AS_PATH was not used to determine the best path -> Answers A and answer C are not correct. All the paths in the output have metric of 0 and this is the lowest (best) value for this attribute. If we configure higher MED then it is less preferred over other paths -> Answer B is not correct. Only answer D is left but LOCAL_PREF attribute should be configured with higher value to be preferred so we hope “lower LOCAL_PREF” here means higher value. But this is the best answer
From the output, we learn that the current best path is from 10.57.255.11 (which includes “...valid, confed-external, best“) and this path is 2 ASes away (64955 65003). Although there are some paths with only 1 AS away (path from 172.16.254.234 for example) but they were not chosen the best path, so AS_PATH was not used to determine the best path. Answers A and answer C are not correct.
can someone explain
Output shows #9 different possible paths. local routers has chosen #6 as best-path. it is asked to what is needed to make path #5 the best-path. - A - wrong (lower MED is preferred.) - B - correct (by adding extra AS_PATH makes the current best-path #6 less preferred compared to route #5) - C - wrong (this is the opposite of B) - D - wrong (higher LOCAL_PREF is preferred not lower!)