HP HPE FlexNetwork 7500 series User Manual

196
The ORIGIN attribute specifies the origin of BGP routes. This attribute has the following types:
 IGP—Has the highest priority. Routes generated in the local AS have the IGP attribute.
 EGP—Has the second highest priority. Routes obtained through EGP have the EGP
attribute.
 INCOMPLETE—Has the lowest priority. The source of routes with this attribute is unknown.
Routes redistributed from other routing protocols have the INCOMPLETE attribute.
•
AS_PATH
The AS_PATH attribute identifies the ASs through which a route has passed. Before
advertising a route to another AS, BGP adds the local AS number into the AS_PATH attribute,
so the receiver can determine ASs to route the message back.
The AS_PATH attribute has the following types:
 AS_SEQUENCE—Arranges AS numbers in sequence. As shown in Figure 51, the number
of the AS closest to the receiver's AS is leftmost.
 AS_SET—Arranges AS numbers randomly.
Figure 51 AS_PATH attribute
BGP uses the AS_PATH attribute to implement the following functions:
 Avoid routing loops—A BGP router does not receive routes containing the local AS
number to avoid routing loops.
 Affect route selection—BGP gives priority to the route with the shortest AS_PATH length if
other factors are the same. As shown in Figure 51, the BGP router in AS 50 gives priority to
the route passing AS 40 for sending data to the destination 8.0.0.0. In some applications,
you can apply a routing policy to control BGP route selection by modifying the AS_PATH
length. For more information about routing policy, see "Configuring routing policies."
 Filter routes—By using an AS path list, you can filter routes based on AS numbers
contained in the AS_PATH attribute. For more information about AS path list, see
"Configuring routing policies."
•
NEXT_HOP
The NEXT_HOP attribute may not be the IP address of a directly connected router. Its value is
determined as follows:
 When a BGP speaker advertises a self-originated route to a BGP peer, it sets the address of
the sending interface as the NEXT_HOP.
8.0.0.0
AS 10
D = 8.0.0.0
AS_PATH = 10
D = 8.0.0.0
AS_PATH = 10
AS 20
AS 40
D = 8.0.0.0
AS_PATH = 20, 10
AS 30
AS 50
D = 8.0.0.0
AS_PATH = 30, 20, 10
D = 8.0.0.0
AS_PATH = 40, 10

HP HPE FlexNetwork 7500 series Specifications

General

Brand	HP
Model	HPE FlexNetwork 7500 series
Category	Switch
Language	English