Figure 6 Automatic Abr Selection For Inter-Area Lsp - Nokia 7705 SAR-W Series Manual

Service aggregation router, mpls

Table of Contents

MPLS and RSVP-TE

CSPF for an inter-area LSP operates as follows:

Automatic ABR Selection for Inter-Area LSP

LSP path empty

Computed ERO: P1[S],

ABR1_1[S], PE2[L]

1. CSPF in the ingress LER node determines that an LSP is inter-area by

performing a route lookup with the destination address of a point-to-point LSP,

such as the address in the "to" field of the LSP configuration. If there is no

intra-area route to the destination address, the LSP is considered to be

2. When the path of the LSP is empty, CPSF computes a single-segment, intra-

area path to an ABR that advertised a prefix matching the destination address

3. If the path of the LSP contains one or more hops, CSPF computes a multi-

segment, intra-area path including the hops that are in the area of the ingress

4. If all hops are in the area of the ingress LER, the calculated path ends on an ABR

that advertised a prefix matching the destination address of the LSP.

5. When there are one or more hops that are not in the area of the ingress LER,

the calculated path ends on an ABR that advertised a prefix matching the first-

hop address that is not in the area of the ingress LER.

Use subject to Terms available at: www.nokia.com

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