Exam 350-501 topic 1 question 78 discussion

I'd say B because accepted should have community value 65001:200

C is wrong because has "and" instead of "or" in the first if, but will also allow any other prefixes D is also wrong because of the "done" action A will allow any other prefixes B is the right answer

Answers “B” is the only one that meet all requirement. Answer “A” and “C” let pass other routes than the requested /48. Answer “C” also has the “and” in the first “if” that is wrong. Answer “D” has that odd “>” symbol and the “done” statement the avoids adding the community to the route. https://www.cisco.com/c/en/us/td/docs/routers/xr12000/software/xr12k_r4-0/routing/configuration/guide/rc40xr12k_chapter7.html The done statement indicates that the action to take is to stop executing the policy and accept the route. When encountering a done statement, the route is passed and no further policy statements are executed. All modifications made to the route prior to the done statement are still valid.

B is the Correct answer

Pass – prefix allowed if not later dropped pass grants a ticket to defeat default drop Execution continues after pass Set – value changed, prefix allowed if not later dropped Any set at any level grants a ticket Execution continues after set Values can be set more than once Done – prefix allowed, stop execution Drop – prefix is discarded Explicit drop stops policy execution Implicit drop (if policy runs to end without getting a ticket)

the answer on the site is wrong. should be B

By process of elimination A: the command set community is outside all of the if validations, so a prefix different from 2001:db8:aaaa::/48, could still pass if it is not discarded in the validations that came before. C: Also has the set community outside the if validations. Also fails due to having the AND keyword, any of the conditions by themselves should discard a prefix. D: worse of all, the DONE keyword will inmediately exit the route-policy without changing the community.

I was doing logic on paper and B is the solution for me, all other choices would violate one or more policy items

I believe the correct answer is A, and here is my reasoning (RULE OUT C & D) We know the default behavior of XR is to DROP, therefor you must define a policy to PASS the traffic IN. [A] shows that PASS is nested within the destination match statement. Therefor it will only pass what it has matched on, as for the community it is global therefor will apply to all matches in the policy. As for B, the destination matches on 2001:db8:aaaa::/48, but as stated previously it does not PASS. So it will enter the ADJ-RIB IN and apply the community but will not PASS therefor it does not enter the LOC-RIB / BGP TABLE