The exhibit shows a BGP multihomed network connecting to ISP A and ISP B. The secondary link
is to be used only in a failover scenario in which the primary link is not usable. Which BGP
attribute should you use to influence inbound traffic to use the primary link t hat is sourced from
ISP C?
A.
multiple exit discriminator (MED)
B.
local preference
C.
AS path
D.
origin
correct answer should be A – MED.
@Jamal312: Wrong, MED is only sent to directly adjacent AS’es, in this case the AS of ISP-A and ISP-B. The MED will be reflected in BGP UPDATE messages from ISP-A or ISP-B to ISP-C since it is a nontransitive attribute. In order to influence inbound routing from non directly adjacent AS’es, AS-PATH can be used.
One would then use AS-PATH prepending to make the secondary link less preferred.