R21xx-HP FlexFabric 11900 MPLS Configuration Guide

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Figure 42 Application of BGP AS number substitution
In Figure 42, both Site and Site 2 use the AS number 800. AS number substitution is enabled on PE 2 for
CE 2. Before advertising updates received from CE 1 to CE 2, PE 2 substitutes its own AS number 100
for the AS number 800. In this way, CE 2 can correctly receive the routing information from CE 1.
However, the AS number substitution function also introduces a routing loop in Site 2 because route
updates originated from CE3 can be advertised back to Site 2 through PE 2 and CE2. To remove the
routing loop, you can configure a routing policy on PE2 to add the SoO attribute to route updates
received from CE 2 and CE 3 so that PE 2 does not advertise route updates from CE 3 to CE 2.
MPLS L3VPN configuration task list
Tasks at a
g
lance
Configuring basic MPLS L3VPN
Configuring inter-AS VPN
Configuring nested VPN
Configuring HoVPN
Specifying the VPN label processing mode on the egress PE
Configuring BGP AS number substitution
Configuring basic MPLS L3VPN
Tasks at a
g
lance
Configuring VPN instances:
1. (Required.) Creating a VPN instance
2. (R
equired.) Associating a VPN instance with an interface
3. (Opti
onal.) Configuring route related attributes for a VPN instance
(Required.) Configuring routing between a PE and a CE
(Required.) Configuring routing between PEs
(Optional.) Configuring BGP VPNv4 route control
MPLS backbone
VPNv4_Update: 10.1.0.0/16
RD: 100:1
AS_PATH: 800
EBGP_Update: 10.1.0.0/16
AS_PATH: 100, 100
PE 1 PE 2
CE 3
AS 800
Site 2
EBGP_Update: 10.1.0.0/16
AS_PATH: 800
AS 800
Site 1
AS 100
CE 1
CE 2