Click the Exhibit button.
Referring to the exhibit, you control AS 24652. You are asked to ensure that traffic destined to the
23.56.83.0/24 network from ISP 4 takes the most optimum path through ISP 3. ISP 1 should be used as a
backup for this traffic flow.
Which two actions would accomplish this task? (Choose two.)
A.
Set a higher local preference for the route advertised by ISP 3.
B.
Advertise a longer AS path from R2 to ISP 4.
C.
Set a lower local preference for the route advertised by ISP 3.
D.
Advertise a longer AS path from R1 to ISP4.
Explanation:
A: Internal BGP (IBGP) sessions use a metric called the local preference, which is carried in IBGP update
packets in the path attribute LOCAL_PREF. When an autonomous system (AS) has multiple routes to another
AS, the local preference indicates the degree of preference for one route over the other routes. The route with
the highest local preference value is preferred.
D: BGP does not take bandwidth into consideration when determining the best path. By using AS path
prepending, you can lengthen the AS path that routing devices advertise to neighbors to make the neighbors
calculate the path to be longer than it actually is.https://www.juniper.net/documentation/en_US/junos15.1/topics/topic-map/bgp-local-preference.html
http://www.juniper.net/documentation/en_US/junos15.1/topics/example/routing-policy-security-routing-policy-toprepend-to-as-path-configuring.html