Which two statements about BGP facilitate the prevention of routing loops between two autonomous systems? (Choose two.)

The correct answer is A. EBGP routers will append their AS number when advertising routes to their neighbors. C. EBGP routers will drop routes that contain their own AS number in the AS_PATH. When an EBGP router advertises a route to a neighbor in a different AS, it appends its own AS number to the AS_PATH attribute. This helps other routers recognize the path the route has taken and prevents routing loops. If an EBGP router receives a route advertisement that…

BGP

Question

Options

AEBGP routers will append their AS number when advertising routes to their neighbors.
BEBGP routers will only accept routes that contain their own AS number in the AS_PATH.
CEBGP routers will drop routes that contain their own AS number in the AS_PATH
DEBGP routers will prepend their AS number when advertising routes to their neighbors

How the community answered

(29 responses)

A
72% (21)
B
10% (3)
D
17% (5)

Explanation

When an EBGP router advertises a route to a neighbor in a different AS, it appends its own AS number to the AS_PATH attribute. This helps other routers recognize the path the route has taken and prevents routing loops. If an EBGP router receives a route advertisement that already contains its own AS number in the AS_PATH attribute, it will drop the route. This prevents the router from accepting a route that would create a routing loop.

Topics

#BGP loop prevention#AS_PATH attribute#EBGP route filtering#AS number prepend

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