Your company has multiple upstream BGP connections to the Internet ISP-A, ISP-B, and ISP-C. You want to
ensure that all traffic coming into your network uses ISP-A.
How would you accomplish this task?
A.
Change the route preference to be higher on routes being advertised to ISP-B and ISP-C.
B.
Prepend your AS number on routes being advertised to ISP-B and ISP-C.
C.
Change the local preference to be higher on routes being advertised to ISP-A.
D.
Prepend your AS number on routes being advertised to ISP-A.
Explanation:
Understanding BGP Path Selection
For each prefix in the routing table, the routing protocol process selects a single best path. After the best path is
selected, the route is installed in the routing table. The best path becomes the active route if the same prefix is
not learned by a protocol with a lower (more preferred) global preference value, also known as the
administrative distance. The algorithm for determining the active route is as follows:
1. Verify that the next hop can be resolved.
2. Choose the path with the lowest preference value (routing protocol process preference).
Routes that are not eligible to be used for forwarding (for example, because they were rejected by routing policy
or because a next hop is inaccessible) have a preference of –1 and are never chosen.
Etc.
https://www.juniper.net/documentation/en_US/junos12.3/topics/reference/general/routingptotocols-address-representation.html