Mpls L3Vpn Frr - HP FlexNetwork HSR6600 Configuration Manual

The BGP AS number substitution feature allows geographically different CEs to use the same AS
number. If the AS_PATH of a route contains the AS number of a CE, the PE replaces the AS number
with its own AS number before advertising the route to that CE.
After you enable the BGP AS number substitution feature, the PE performs BGP AS number
substitution for all routes and re-advertises them to connected CEs in the peer group.
Figure 67 Application of BGP AS number substitution and SoO attribute
EBGP_Update: 10.1.0.0/16
AS_PATH: 800
AS 800
Site 1
As shown in
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 feature also introduces a routing loop in Site 2 because route
updates originated from CE 3 can be advertised back to Site 2 through PE 2 and CE 2. To remove
the routing loop, you can configure the same SoO attribute on PE 2 for CE 2 and CE 3. PE 2 adds the
SoO attribute to route updates received from CE 2 or CE 3, and checks the SoO attribute of route
updates to be advertised to CE 2 or CE 3. The SoO attribute of the route updates from CE 3 is the
same as the SoO attribute for CE 2, and PE 2 does not advertise route updates to CE 2.
For more information about the SoO attribute, see Layer 3—IP Routing Configuration Guide.

MPLS L3VPN FRR

MPLS L3VPN Fast Reroute (FRR) is applicable to a dual-homed scenario, as shown in
using BFD to detect the primary link, FRR enables a PE to use the backup link when the primary link
fails. The PE then selects a new optimal route, and uses the new optimal route to forward traffic.
MPLS L3VPN FRR supports the following types of backup:
•
VPNv4 route backup for a VPNv4 route.
•
VPNv4 route backup for an IPv4 route.
•
IPv4 route backup for a VPNv4 route.
VPNv4 route backup for a VPNv4 route
As shown in
VPN 1 as PE 3. When PE 1 receives a VPNv4 route to CE 2 from both PE 2 and PE 3, it uses the
route from PE 2 as the primary link, and the route from PE 3 as the backup link.
PE 1
VPNv4_Update: 10.1.0.0/16
RD: 100:1
AS_PATH: 800
CE 1
Figure 67, both Site 1 and Site 2 use the AS number 800. AS number substitution is
Figure 68, configure FRR on the ingress node PE 1, and specify the backup next hop for
AS 100
PE 2
MPLS backbone
213
CE 3
AS 800
Site 2
EBGP_Update: 10.1.0.0/16
AS_PATH: 100, 100
CE 2
Figure 68. By