Juniper JUNOSE 11.2.X BGP AND MPLS, Configuration Manual

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outbound route map to filter routes; for more information, see Extended Community Lists
in the JunosE IP Services Configuration Guide .
Alternatively, you can use the neighbor site-of-origin command alone to achieve the
same effect in such a network configuration. Consider the network shown in Figure 96
on page 449, which enables PE 3 to advertise back to CE 1 routes that it learned from PE
1 that originated with CE 1. In a typical network configuration, CE 1 rejects these routes
because it determines from the AS path that a routing loop exists. In this particular
network, the
neighbor as-override command prevents this method of detection.
Figure 96: Network with Potential Routing Loops
The following commands are relevant to the illustrated network:
host1:pe1(config)# ip vrf yourvpn
host1:pe1(config-vrf)# rd 200:1
host1:pe1(config-vrf)# route-target both 200:11
...
host1:pe1(config)#
router bgp 200
host1:pe1(config-router)# address-family ipv4 unicast vrf yourvpn
host1:pe1(config-router)# neighbor 10.5.4.22 remote-as 100
host1:pe1(config-router)# neighbor 10.5.4.22 as-override
...
Now, suppose instead you assign a unique site of origin to each CE router in the network
and configure the BGP session on each PE router with the site of origin. The result of the
following (partial) configuration is shown in Figure 97 on page 450.
host1:pe1(config)# ip vrf yourvpn
host1:pe1(config-vrf)# rd 200:1
host1:pe1(config-vrf)# route-target both 200:11
...
449 Copyright © 2010, Juniper Networks, Inc.
Chapter 6: Configuring BGP-MPLS Applications