640-802 Braindump, 350-001 Exam and VCP-310

When influencing incoming traffic from the Internet, the two most widely used methods
are AS Path Prepending and Multi-Exit Discriminators (MED). AS Path prepending
works by adding AS paths to VCP-310
certain network ranges, making them appear to the Internet
to be further away than they really are. MEDs are used to advertise metrics to the
neighbor AS to influence the incoming path that traffic should take to reach certain
destinations. In this case, AS Path Prepending is preferred over the use of MEDs because
AS path prepending information is distributed to all networks within the Internet. MEDs
are only used between neighboring Autnomous Systems. Another advantage to path
prepending is that the AS path information is ranked higher in the BGP decision process
than the MED information.350-001
IN fact, MED information is one of the last things considered
in the BGP path decision algorithm. There is sometimes confusion between the two Border Gateway Protocol (BGP)
configuration commands bgp deterministic-med and bgp always-compare-med.
Enabling the bgp deterministic-med command ensures the comparison of the MED
variable when choosing routes advertised by different peers in the same autonomous
system. Enabling the bgp always-compare-med command ensures the comparison of the
MED for paths from neighbors in different autonomous systems. The bgp
always-compare-med command is useful when multiple service providers or enterprises
agree on a uniform policy for setting MED. Thus, for network X, if Internet Service
Provider A (ISP A) sets the MED to 10, and ISP B sets the MED to 20, both ISPs agree
that ISP A has the better performing path to X.640-802
When BGP receives multiple routes to a particular destination, it lists them in the reverse
order that they were received, from the newest to the oldest. BGP then compares the
routes in pairs, starting with the newest entry and moving toward the oldest entry
(starting at top of the list and moving down). For example, entry1 and entry2 are
compared. The better of these two is then compared to entry3, and so on.