PBR to an LSP
Policy-based routing (PBR) enables a device to select routes based on a user-defined policy, which helps transmit traffic securely or balance traffic. On an MPLS network, IP packets that meet a PBR policy can be forwarded along a specified LSP. Figure 1 illustrates an MPLS network on which PBR is used.
On the network shown in Figure 1, DeviceF and DeviceG are added to a legacy network to provide new services. To allow part of the new services to pass through the original network, the PBR can be configured on DeviceA. The services that meet a specific PBR policy can travel along LSPs over the original network.
The traffic for original services is forwarded through the original network.
The traffic for new services is forwarded by DeviceF and DeviceG.
To forward part of the traffic of new services through the original network, you can configure the PBR to an LSP on DeviceA. The traffic matching the specific policy can be forwarded through the original network.
You can also use PBR with LDP fast reroute (FRR) to divert some traffic to a backup LSP to balance traffic between the primary and backup LSP may be idle relatively.