How Mpls Lsp Monitoring Works; Bgp Next-Hop Neighbor Discovery - Cisco ASR 9000 Serie Configuration Manuals

MPLS LSP Monitoring
To use the MPLS LSP monitor feature, you must understand these concepts:

How MPLS LSP Monitoring Works

The MPLS LSP monitor feature provides the capability to proactively monitor Layer 3 MPLS VPNs. The
general process for how the MPLS LSP monitor works is as follows:
1 The user configures an MPLS LSP monitor instance.
Configuring an MPLS LSP monitor instance is similar to configuring a standard IP SLA operation. To
illustrate, all operation parameters for an MPLS LSP monitor instance are configured after an identification
number for the operation is specified. However, unlike standard IP SLA operations, these configured
parameters are then used as the base configuration for the individual IP SLA LSP ping and LSP traceroute
operations that will be created by the MPLS LSP monitor instance.
When the first MPLS LSP monitor instance is configured and scheduled to begin, BGP next-hop neighbor
discovery is enabled. See the
2 The user configures proactive threshold violation monitoring for the MPLS LSP monitor instance.
3 The user configures multioperation scheduling parameters for the MPLS LSP monitor instance.
4 Depending on the configuration options chosen, the MPLS LSP monitor instance automatically creates
individual IP SLA LSP ping or LSP traceroute operations for each applicable BGP next-hop neighbor.
For any given MPLS LSP monitor operation, only one IP SLA LSP ping or LSP traceroute operation is
configured per BGP next-hop neighbor. However, more than one MPLS LSP monitor instance can be
running on a particular PE router at the same time. (For more details, see the note at the end of this section.)
5 Each IP SLA LSP ping or LSP traceroute operation measures network connectivity between the source
PE router and the discovered destination PE router.
Note More than one MPLS LSP monitor instance can be running on a particular PE router at the same time.
For example, one MPLS LSP monitor instance can be configured to discover BGP next-hop neighbors
belonging to the VRF named VPN1. On the same PE router, another MPLS LSP monitor instance can be
configured to discover neighbors belonging to the VRF named VPN2. In this case, if a BGP next-hop
neighbor belonged to both VPN1 and VPN2, then the PE router would create two IP SLA operations for
this neighbor—one for VPN1 and one for VPN2.
Adding and Deleting IP SLA Operations from the MPLS LSP Monitor Database
The MPLS LSP monitor instance receives periodic notifications about BGP next-hop neighbors that have
been added to or removed from a particular VPN. This information is stored in a queue maintained by the
MPLS LSP monitor instance. Based on the information in the queue and user-specified time intervals, new
IP SLA operations are automatically created for newly discovered PE routers and existing IP SLA operations
are automatically deleted for any PE routers that are no longer valid.

BGP Next-hop Neighbor Discovery

BGP next-hop neighbor discovery is used to find the BGP next-hop neighbors in use by any VRF associated
with the source provider edge (PE) router. In most cases, these neighbors are PE routers.
Cisco ASR 9000 Series Aggregation Services Router System Monitoring Configuration Guide, Release 4.2.x
206
BGP Next-hop Neighbor Discovery , on page
Implementing IP Service Level Agreements
206.