Similar to other FRR technologies, in the VPN FRR, an available bypass path is reserved for
fast switchover before the primary path fails. For VPN FRR, two next hops (PEs) are reserved
for the local device to access the private network. One is the active PE and the other is the standby
PE. The active and standby PEs are configured manually.
As shown in
, PE1 reserves two next hops, that is, PE3 and PE4, to access the remote
VPN. PE1 can select either of them as the active next hop and the standby next hop.
l
Without the VPN FRR, only an active next hop entry is delivered from the control plane
to the forwarding plane. When the active next hop becomes invalid, the standby next hop
entry is delivered to the forwarding plane. As a result, the switchover is slow.
l
After the configuration of VPN FRR, both next hop entries are delivered from the control
plane to the forwarding plane. When the active next hop becomes invalid, the standby next
hop can be applied quickly to the forwarding plane. The switchover speeds up.
After BFD detects that the PE of the active next hop fails, switchover is performed within a very
short period, which ensures high reliability.
1.4.4 Failure of Downlink Interface on the PE - IP FRR
In IP FRR (Fast ReRoute), when a primary path between a CE and a PE fails, traffic can be
switched to a backup path.
Figure 1-6
Networking diagram of IP FRR application
PE1
PE2
CE
MPLS-VPN
Backbone
, the traffic to the CE is forwarded by PE1 (the active PE). If the link
between PE1 and the CE fails, IP FRR switches the traffic from the link between PE1 and the
CE to the link between PE2 to the CE.
The principle of FRR is to retain a bypass path on the forwarding plane for fast switchover.
Similarly, with IP FRR, two paths exist between PE1 and CE. For one path, packets are
transmitted through direct route. For the other path, packets are transmitted from PE1 to PE2
and then forwarded to CE.
HUAWEI NetEngine80E/40E Router
Configuration Guide - Reliability
1 Reliability Overview
Issue 02 (2014-09-30)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
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