350-501 · Question #394
Refer to the exhibit. A network engineer must update the routing toward the web server with IP address 35.22.13.1. The primary path must be configured via the neighbor router with ID 1.1.1.1…
The correct answer is C. Enable MED comparison between routes from neighbors in different AS. To make R1 prefer a specific path to 35.22.13.1 via neighbor 1.1.1.1 without using local-preference, MED can be used to influence path selection. Since MED is only compared between routes from the same AS by default, R1 must be configured to compare MEDs from routes originating…
Question
Refer to the exhibit. A network engineer must update the routing toward the web server with IP address 35.22.13.1. The primary path must be configured via the neighbor router with ID 1.1.1.1. However, local-preference configuration is not permitted on R1. Which task must the engineer perform on R1 to complete the implementation?
Exhibit
Options
- AConfigure the device to choose the best MED from the same AS.
- BSet the device to ignore the conditional MED if the route originated in a different autonomous
- CEnable MED comparison between routes from neighbors in different AS.
- DImplement deterministic MED to choose the best route from the different AS.
How the community answered
(28 responses)- A4% (1)
- B14% (4)
- C75% (21)
- D7% (2)
Why each option
To make R1 prefer a specific path to 35.22.13.1 via neighbor 1.1.1.1 without using local-preference, MED can be used to influence path selection. Since MED is only compared between routes from the same AS by default, R1 must be configured to compare MEDs from routes originating in different ASes.
This describes the default behavior of BGP regarding MED comparison, which is not sufficient if the goal is to compare MEDs from different ASes.
Ignoring conditional MEDs from different ASes would prevent using MED for path selection, which contradicts the goal of influencing the path.
By default, BGP only compares MED values for routes received from neighbors in the same autonomous system. To prefer a specific path using MED when routes originate from different ASes, the `bgp always-compare-med` command must be enabled on R1, allowing MED comparison regardless of the originating AS. This allows the engineer to use MED to select the primary path via 1.1.1.1.
Deterministic MED ensures consistent MED comparison within the same AS when multiple iBGP paths are available, but it does not enable comparison between routes from different ASes.
Concept tested: BGP MED comparison across AS boundaries
Source: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bgp/command/bgp-cr-book/bgp-b1.html#wp2273117565
Topics
Community Discussion
No community discussion yet for this question.