HP MSR Series Configuration Manual page 182

Figure 50 MED attribute
D = 9.0.0.0
Next_hop = 2.1.1.1
MED = 0
Router A
D = 9.0.0.0
Next_hop = 3.1.1.1
MED = 100
AS 10
Generally, BGP only compares MEDs of routes received from the same AS. You can also use the
compare-different-as-med command to force BGP to compare MED values of routes received from
different ASs.
LOCAL_PREF
•
The LOCAL_PREF attribute is exchanged between IBGP peers only, and is not advertised to any
other AS. It indicates the priority of a BGP router.
BGP uses LOCAL_PREF to determine the best route for traffic leaving the local AS. When a BGP
router obtains from several IBGP peers multiple routes to the same destination but with different
next hops, it considers the route with the highest LOCAL_PREF value as the best route. As shown
in Figure 51, traffic from AS 20 to AS 10 travels through Router C that is selected according to
LOCAL_PREF.
MED = 0
Router B
2.1.1.1
EBGP IBGP
IBGP
EBGP IBGP
3.1.1.1
Router C
MED = 100
170
9.0.0.0
Router D
AS 20