MPLS Traffic Engineered tunnel discovery modes

Set the discovery mode according to how much detail you want to retrieve.

A mode-switch is provided in the discovery agent configuration file that configures specific tunnel instances, which can be wildcarded, to retrieve different amounts of tunnel data. You can choose any of the following modes.

HeadEndHops (default)

In HeadEndHops mode, the agent retrieves head-end and tail-end of the tunnel, and the transit LSRs and next-hop interfaces are identified by querying the head-end LSR for computed and actual-route hop data. The actual and computed route data is retrieved from the mplsTunnelARHopTable and mplsTunnelCHopTable MIB tables respectively. This discovery mode does not store transit and tail-end tunnel instances against transit and tail-end LSRs. A connection is created in the MPLS TE topology between the head-end and tail-end LSR interfaces via transit device hops (if present) which are associated with the head-end LSR tunnel object for the appropriate tunnel interface.

MPLS cross-connect pointers that are discovered and resolved on the head tunnel will be resolved to the appropriate LSP ID where possible.

You can use this information to determine if the actual path taken by a tunnel is different to the path computed by the Compute Shortest Path First (CSPF) calculations. You can see the computed and actual path, although there is no way to determine that an LSR is acting in a transit or tail capacity without looking at the head-end LSR tunnel data.

Note: Actual route data is only available if the Record Route Option (RRO) has been specified for the tunnel instance.

In the schema of the scope.mplsTe table, the HeadEndHops mode maps to value 1 of m_Mode.

HeadTailEnd

In HeadTailEnd mode, only MPLS TE tunnel head-end and tail-end points are resolved, by querying the head-end Label Switching Router (LSR). This mode provides the minimal amount of information about the MPLS TE tunnels. A connection in the MPLS TE topology is created between the head-end and tail-end LSR interfaces. A tunnel resource instance is associated with the head-end tunnel LSR entity.

In this mode, you cannot identify the transit LSRs, and computed and actual route data is not retrieved.

MPLS cross-connect pointers that are discovered and resolved on the head tunnel will be resolved to the appropriate LSP ID where possible.

In the schema of the scope.mplsTe table, the HeadTailEnd mode maps to value 2 of m_Mode.

AllLSRTunnelsAndHops

In AllLSRTunnelsAndHops mode, the agent retrieves the head-end and tail-end of the tunnel and identifies transit LSRs and next-hop interfaces by querying the head-end LSR for computed and actual route hop data. The actual and computed route data is retrieved from the mplsTunnelARHopTable and mplsTunnelCHopTable MIB tables respectively. This discovery mode stores transit and tail-end tunnel instances against transit and tail-end LSRs. The mode creates a connection in the MPLS TE topology between the head-end and tail-end LSR interfaces that are associated with the head-end (for the tunnel interface) and transit and tail-end LSR tunnel objects. Computed and actual-route connections are associated with Computed and Actual connection entity types, which are aggregated in sequence from the head-end LSR tunnel entity. A tunnel resource instance is associated with the head-end tunnel LSR entity.

You can use this information to determine if the actual path taken by a tunnel is different to the path computed by the CSPF calculations. You can see the computed and actual path and determine the transit or tail-end role of an LSR without looking at the headend LSR tunnel instance.

Note: Actual route data is only available if the Record Route Option (RRO) has been specified for the tunnel instance.

MPLS cross-connect pointers that are discovered and resolved on the head tunnel will be resolved to the appropriate LSP ID where possible.

In the schema of the scope.mplsTe table, the AllLSRTunnelsAndHops mode maps to value 3 of m_Mode.