hardMultiple Choice
350-401 Practice Question: An engineer is configuring BGP on a router that…
An engineer is configuring BGP on a router that will act as a route reflector to reduce iBGP peering requirements. The router has several iBGP peers. The engineer wants to ensure that the route reflector does not modify the next-hop attribute of routes it reflects to its clients. Which configuration command should the engineer use?
⚠ Common exam trap
Cisco often tests the distinction between 'neighbor next-hop-unchanged' and 'neighbor next-hop-self', where candidates mistakenly think that disabling 'next-hop-self' (option B) is sufficient to preserve the next-hop, but the correct command is the explicit 'next-hop-unchanged' to override any default or configured modifications.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure 'neighbor next-hop-unchanged' under the BGP address family for the route reflector clients.
The 'neighbor next-hop-unchanged' command under the BGP address family instructs the route reflector to preserve the original next-hop attribute when reflecting routes to its clients. By default, a route reflector may modify the next-hop to its own address, but this command overrides that behavior, ensuring the next-hop remains as received from the non-client iBGP peer. This is essential in designs where clients must see the original next-hop for optimal path selection or to avoid unnecessary routing hops.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Configure 'neighbor next-hop-unchanged' under the BGP address family for the route reflector clients.
Why this is correct
Configuring 'neighbor next-hop-unchanged' under the BGP address family for route-reflector clients explicitly tells the router to leave the next-hop attribute untouched when reflecting routes. This is the correct method because it preserves the original next-hop as advertised by the eBGP peer or other source, preventing the route reflector from replacing it with its own address. The command is applied per-neighbor within the address family, and it overrides the default behavior where the router might otherwise modify the next-hop to itself. By doing so, clients learn the true next-hop and can forward traffic optimally without an unnecessary hop through the reflector.
- ✗
Configure 'no bgp next-hop-self' under the BGP address family for the route reflector clients.
Why it's wrong here
Incorrect because 'no bgp next-hop-self' is not a valid command; the correct command is 'no neighbor next-hop-self', but that only removes the configuration that would set next-hop to self; it does not guarantee the next-hop is unchanged if other mechanisms are in place.
- ✗
Configure 'bgp route-reflector' under the BGP address family.
Why it's wrong here
The command 'bgp route-reflector' does not exist in Cisco IOS/IOS-XE; route reflector functionality is enabled per neighbor using 'neighbor [ip-address] route-reflector-client'. There is no single global or address-family command that designates the router as a route reflector and simultaneously defines which clients it serves. Entering an invalid command would be rejected by the CLI, and even if it were accepted, it would not address the specific requirement of preserving the next-hop attribute. The proper configuration requires explicitly identifying each client with the 'route-reflector-client' keyword.
- ✗
Configure 'neighbor next-hop-self' on the route reflector for its clients.
Why it's wrong here
Applying 'neighbor next-hop-self' on the route reflector for its clients would cause the RR to substitute its own IP address as the next-hop for all reflected routes. This directly contradicts the engineer's goal of keeping the original next-hop unchanged, and it would force clients to send traffic through the route reflector, creating suboptimal routing paths and potential extra latency. While 'next-hop-self' is a valid BGP command, it is used in different scenarios where iBGP speakers must advertise routes with themselves as the next-hop to ensure reachability; here, it would deliberately alter the attribute that the engineer wants to preserve.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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