350-501 · Question #454
350-501 Question #454: Real Exam Question with Answer & Explanation
The correct answer is A: Enable no synchronization on R2 m AS65101.. The issue where traffic from R4 doesn't use the R3-R2-R1 path for 192.168.1.1/32, despite R1 advertising the route, is likely caused by BGP synchronization being enabled on R2. Disabling synchronization (no synchronization) on R2 will allow it to install and advertise the iBGP-le
Question
Refer to the exhibit. All BGP peering in AS 65101 and 65201 is enabled. The operations team is told that traffic destined to 192.168.1.1/32 from R4 does not use the path R3-R2-R1 as expected. An engineer debugs the issue and determines that 192.168.1.1/32 is advertised in the BGP routing table on R1. Which action resolves the issue?
Options
- AEnable no synchronization on R2 m AS65101.
- BApply route-map High-LP out for prefix 192.168.1.1/32 on R1 with R2 BGP peering.
- CApply redistribute ospf 10 on R1 in BGP AS 65101.
- DConfigure network 192.168.1.1 mask 255.255.255.255 in BGP AS 65101 on R2
Explanation
The issue where traffic from R4 doesn't use the R3-R2-R1 path for 192.168.1.1/32, despite R1 advertising the route, is likely caused by BGP synchronization being enabled on R2. Disabling synchronization (no synchronization) on R2 will allow it to install and advertise the iBGP-learned route from R1 even if it's not present in its IGP, enabling the expected traffic path.
Common mistakes.
- B. Applying a route-map to modify Local Preference on R1 for R2 peering affects how R2 perceives routes learned from R1, primarily influencing path selection within the local AS, but it does not address the fundamental issue of R2 failing to install or advertise an iBGP-learned route due to synchronization.
- C. The problem states that 192.168.1.1/32 is already advertised in R1's BGP table, meaning R1 is successfully originating the route into BGP. Redistributing OSPF into BGP on R1 would not resolve a synchronization issue on R2 for a route already in BGP.
- D. Configuring a
networkstatement on R2 for 192.168.1.1/32 would make R2 originate the route into BGP, potentially creating a different path, but it does not address why the existing route from R1 is not being utilized or propagated by R2, and it changes the point of origin.
Concept tested. BGP synchronization rule
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