HPE 5800 Series Configuration Manual page 181

Implements route filtering—By configuring an AS path filtering list, you can filter routes
based on AS numbers contained in the AS_PATH attribute. For more information about
routing policies and AS path filtering lists, see
•
NEXT_HOP
The NEXT_HOP attribute is not necessarily the IP address of a directly connected router. It
involves the following types of values, as shown in
When advertising a self-originated route to all BGP peers, a BGP speaker sets the
NEXT_HOP for the route to the address of its sending interface.
When sending a received route to an EBGP peer, a BGP speaker sets the NEXT_HOP for
the route to the address of the sending interface.
When sending a route received from an EBGP peer to an IBGP peer, a BGP speaker does
not modify the NEXT_HOP attribute. If load balancing is configured, the NEXT_HOP
attribute of the equal-cost routes is modified. For information about load balancing, see
"BGP load balancing."
Figure 58 NEXT_HOP attribute
•
MED (Multi-Exit Discriminator)
The MED attribute is exchanged between two neighboring ASs, each of which does not
advertise the attribute to any other AS.
Similar to metrics used by IGP, MED is used to determine the best route for traffic going into an
AS. When a BGP router obtains multiple routes to the same destination but with different next
hops from different EBGP peers, it considers the route with the smallest MED value the best
route given that other conditions are the same. As shown in
20 travels through Router B that is selected according to MED.
"Configuring routing
Figure 58.
170
policies."
Figure 59, traffic from AS 10 to AS