Exam 300-420 topic 1 question 204 discussion

In multipoint two-way redistribution scenarios with EIGRP and a distance vector protocol like RIPv1, you need to prevent the distance vector protocol (RIPv1 in this case) from re-advertising routes learned from EIGRP back into EIGRP. This is achieved by applying an inbound distribute-list on the RIPv1 process, filtering out the EIGRP-learned prefixes.

It's C - think AD. EIGRP routes learned via RIP, won't be a problem (90 vs EX 170). So no worries about EIGRP routes looping. Now RIP - Internal and external routes got an AD of 120 so we should filter these RIP routes from coming back via EIGRP - So Distribute out... people saying A --> You're right it RIP routes won't loop because you won't have any rip routes at all. Basically, you just redistribute one way!

my exam in 50 minutes and my head is full of info but here is what I think of this question....since RIPv1 is classful protocol, there is no fear of loops caused by EIGRP routes being advertised back to EIGRP because the only thing that will be advertised back to EIGRP is the classful EIGRP 10.0.0.0 and the classful RIPv1 192.168.x.0 routes. The fear is RIPv1 routes coming back to RIP through EIGRP. So the answer in this case is D....under rip, distribute-list out preventing redistributed RIPv1 routes in EIGRP coming back to RIP. so Answer is D.....to the exam...wish you all the best of luck

distribute-lists inbound under the EIGRP process denying RIPv1 learned prefixes

Not sure which is the correct one. But, I assume that R2 and R3 are core routers for R4 and R5. For me, make sense Answer C: Filter out under EIGRP the learned prefix from RIP. R2 and R3 will have on their routing table, both, RIP and EIGRP routes, and they are able to reach all sites. A is not suitable, because you are filtering a network that never should be advertised. It spend more resources. B is not suitable, because R2 and R3 will never learn the networks from RIP. D is not suitable, because then R1 will never will be able to learn networks from EIGRP. So, for me C could be a good aproach.

A. distribute-lists inbound under the EIGRP process denying RIPv1 learned prefixes Using distribute-lists inbound under the EIGRP process, you can filter out the RIPv1 learned prefixes. This prevents the prefixes learned via RIPv1 from being redistributed back into EIGRP, thus avoiding potential routing loops during the redistribution process.

Answer is A.. just labbed this

I think that the key point is knowing where to put the config. For instance, if it was on R2 and R3, both R2 and R3 would be redistributing the rip route for . What you want to do is block that route that is being received from R4 and R5 and being redistributed back into R2 and R3. I think is like the following question: https://www.examtopics.com/discussions/cisco/view/85755-exam-300-410-topic-1-question-235-discussion/