Exam 350-401 topic 1 question 168 discussion

A. R3(config)#route-map PREPEND permit 10 R3(config-route-map)#set as-path prepend 200 200 200 R3(config)#router bgp 200 R3#(config-router)#neighbor 10.1.1.1 route-map PREPEND out B. R4(config)#route-map PREPEND permit 10 R4(config-route-map)#set as-path prepend 100 100 100 R4(config)#router bgp 200 R4(config-router)#neighbor 10.2.2.2 route-map PREPEND in C. R4(config)#route-map PREPEND permit 10 R4(config-route-map)#set as-path prepend 200 200 200 R4(config)#router bgp 200 R4(config-router)#neighbor 10.2.2.2 route-map PREPEND out D. R3(config)#route-map PREPEND permit 10 R3(config-route-map)#set as-path prepend 100 100 100 R3(config)#router bgp 200 R3(config-router)#neighbor 10.1.1.1 route-map PREPEND in

A for sure! R3 prepends its AS and sends it outbound to R1 in AS 100. Because R1 and R2 are in one iBGP domain (AS 100), all traffic from AS 100 will prefer to use a shorter AS path to AS 200 which is R4's link.

A is correct

I got this one wrong and selected D because I remembered similar Q139 and misread this question that we want AS100 to choose link 2, and not AS 200 choose link 2. But now that I read these discussions, realized I had the traffic direction backwards, in which case answer is definitely A.

What is AS path Prepending? In the Border Gateway Protocol (BGP), prepending is a technique used to deprioritize a route by artificially increasing the length of the AS-PATH attribute by repeating an autonomous system number (ASN). Route selection in BGP prefers the shorter AS path length, assuming all other criteria are equal

hi! why is the route map PREPEND applied on R3 , out ? Thanks Regards

A is the correct option, you add your own AS in the AS Path to make it "look bad".

what is the meaning of permit 10 ?

A is correct

Correct Answer is A A. R3(config)#route-map PREPEND permit 10 R3(config-route-map)#set as-path prepend 200 200 200 R3(config)#router bgp 200 R3#(config-router)#neighbor 10.1.1.1 route-map PREPEND out B. R4(config)#route-map PREPEND permit 10 R4(config-route-map)#set as-path prepend 100 100 100 R4(config)#router bgp 200 R4(config-router)#neighbor 10.2.2.2 route-map PREPEND in C. R4(config)#route-map PREPEND permit 10 R4(config-route-map)#set as-path prepend 200 200 200 R4(config)#router bgp 200 R4(config-router)#neighbor 10.2.2.2 route-map PREPEND out D. R3(config)#route-map PREPEND permit 10 R3(config-route-map)#set as-path prepend 100 100 100 R3(config)#router bgp 200 R3(config-router)#neighbor 10.1.1.1 route-map PREPEND in

XZIOMAL9, thank you for the formatting; the original presentation of the potential answers is abysmal!

>>xziomal9 thank you very much!!

Given answer is correct