The vprn-target action is a resilient redirection capability which combines both data-path and control plane lookups to achieve the needed redirection. It allows for the following redirection models:
redirection toward the default PE while selecting a specific LSP to use
redirection toward an alternative PE while selecting or not a specific LSP to use. If a specific LSP is not selected, then the system automatically selects one based on the BGP next-hop tunnel resolution mechanism
all of the above within any VPRN
When configuring this action, the user must specify the target BGP next-hop (bgp-nh) toward the redirection that should occur, as well as the routing context (router) in which the necessary lookups are performed (to derive the service label).
The target BGP next-hop can be configured with any label allocation method (label per VRF, label per next-hop, label per prefix). These methods entail different forwarding behaviors; however, the steering node is not aware of the configuration of the target node. If the user does not specify an advertised route prefix (adv-prefix), the steering node assumes that label per VRF is used by the target node and selects the service label accordingly. If the target node is not operating according to the label per VRF method, the user must specify an appropriate route prefix for which a service label is advertised by the target node, keeping in mind the resulting forwarding behavior at the target node of the redirected packet. This specification instructs the steering node to use that specific service label.
Be aware that the system performs and exact match between the specified ip-address/mask (or ipv6-address/prefix-length) and the advertised route.
The user can specify an LSP (RSVP-TE, MPLS-TP, or SR-TE LSP) to use toward the BGP next-hop. If no LSP is specified, the system automatically selects one the same way it would have done when normally forwarding a packet toward the BGP next-hop.
While the system only performs the redirection when the traffic is effectively able to reach the target BGP next-hop, it does not verify whether the redirected packets effectively reach their destination after that.
This action is resilient in that it tracks events affecting the redirection at the service level and reacts to those events. The system performs the redirection as long as it can reach the target BGP next-hop using the correct service label. If the redirection cannot be performed (for example, if no LSP is available, the peer is down, or there is no more specific labeled route), the system reverts to normal forwarding. This can be overridden and configured to drop. A maximum of 8k of unique (3-tuple {bgp-nh, router, adv-prefix}) redirection targets can be tracked.