Figure 96: Network With Potential Routing Loops - Juniper JUNOSE SOFTWARE FOR E SERIES 11.3.X - BGP AND MPLS CONFIGURATION GUIDE 2010-10-12 Configuration Manual

JunosE 11.3.x BGP and MPLS Configuration Guide

Figure 96: Network with Potential Routing Loops

452
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 452, 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.
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 453.
host1:pe1(config)#ip vrf yourvpn
host1:pe1(config-vrf)#rd 200:1
host1:pe1(config-vrf)#route-target both 200:11
...
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