Referring to the exhibit, which two statements are correct? (Choose two.)

The correct answer is A. Devices in AS 65512 will prefer ISP A for traffic destined to the 172.20.21.0/24 network. B. Devices In AS 65512 will prefer ISP A for traffic destined to the 172.20.0.0/24 network. Local preference is a BGP attribute that dictates which path is preferred when multiple paths to the same destination are available. A higher local preference is preferred over a lower one. Since ISP A (AS 65501) is advertising a local preference of 100 and ISP B (AS 65502) is…

BGP

Question

Exhibit

Options

ADevices in AS 65512 will prefer ISP A for traffic destined to the 172.20.21.0/24 network.
BDevices In AS 65512 will prefer ISP A for traffic destined to the 172.20.0.0/24 network.
CDevices in AS 65512 will prefer ISP B for traffic destined to the 172.20.21.0/24 network.
DDevices In AS 65512 will prefer ISP B for traffic destined to the 172.20.0.0/24 network.

How the community answered

(15 responses)

A
73% (11)
C
7% (1)
D
20% (3)

Explanation

Local preference is a BGP attribute that dictates which path is preferred when multiple paths to the same destination are available. A higher local preference is preferred over a lower one. Since ISP A (AS 65501) is advertising a local preference of 100 and ISP B (AS 65502) is advertising a local preference of 200 to AS 65512, traffic from devices in AS 65512 will prefer the path via ISP B for all networks that ISP B advertises. However, since ISP A advertises the 172.20.21.0/24 network and ISP B does not, traffic for 172.20.21.0/24 will go through ISP A. For the 172.20.0.0/24 network, which both ISPs advertise, devices in AS 65512 will prefer the path via ISP B due to the higher local preference.

Topics

#BGP route selection#ISP traffic preference#route specificity#longest prefix match

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