Table 20: Origin And As Path For Routes Viewed On Different Routers - Juniper JUNOSE SOFTWARE FOR E SERIES 11.0.X - BGP AND MPLS CONFIGURATION GUIDE 2009-12-30 Configuration Manual

Consider how route 172.21.10.0/23 is passed along to the routers in Figure 33 on
page 118:
IS-IS injects route 172.21.10.0/23 from router Chicago into BGP on router LA.
1.
BGP sets the origin attribute to Incomplete (because it is a redistributed route)
to indicate how BGP originally became aware of the route.
Router Boston learns about route 172.21.10.0/23 by means of EBGP from router
2.
LA.
Router NY learns about route 172.21.10.0/23 by means of IBGP from router
3.
Boston.
The value of the origin attribute for a given route remains the same, regardless of
where you examine it. Table 20 on page 119 shows this for all the routes known to
routers NY and LA.

Table 20: Origin and AS Path for Routes Viewed on Different Routers

Route Router
192.168.204.0/22 Albany
192.168.204.0/22 Boston
192.168.204.0/22 NY
192.168.204.0/22 LA
172.21.10.0/23 Albany
172.21.10.0/23 Boston
172.21.10.0/23 NY
172.21.10.0/23 LA
172.28.8.0/21 Albany
172.28.8.0/21 Boston
172.28.8.0/21 NY
172.28.8.0/21 LA
172.31.125.100 Albany
172.31.125.100 Boston
172.31.125.100 NY
172.31.125.100 LA
172.19.0.0/16 Albany
172.19.0.0/16 Boston
Chapter 1: Configuring BGP Routing
Origin AS Path
IGP 300
IGP 300
IGP 300
IGP empty
Incomplete 300
Incomplete 300
Incomplete 300
Incomplete empty
IGP empty
IGP empty
IGP empty
IGP 100
Incomplete empty
Incomplete empty
Incomplete empty
Incomplete 100
IGP empty
IGP empty
Selecting the Best Path
119