Based on the VPRN BGP decision process, which of the following routes is selected first if the command "PE1>config>service>vprn> bgp best-path-selection as-path-ignore" is executed?

The standard BGP best-path selection algorithm prefers the route with the shortest ASPATH length. The command best-path-selection as-path-ignore explicitly modifies this behavior, instructing the BGP process to skip the ASPATH length comparison step. According to the Nokia SR OS BGP decision process, the step immediately following the ASPATH check is the evaluation of the ORIGIN attribute. Therefore, with the ASPATH check ignored, the router will next prefer the route with the lowest ORIGIN code (where IGP is lower than EGP, which is lower than INCOMPLETE).

A. The preference for an eBGP-learned route over an iBGP-learned route occurs later in the decision process, after the ORIGIN attribute has already been evaluated.
C. The originator ID or BGP Identifier is used as a final tie-breaker much later in the selection process if all preceding attributes are identical.
D. This option is incorrect because the as-path-ignore command specifically instructs the BGP process to skip the evaluation of the AS path length.

1. Nokia 7750 SR OS R21.10.R1 Services Guide, Document Part Number: 3HE 17675 AAAC TQZZA, Edition 01.

Section: VPRN Services > BGP for VPRN > BGP Path Selection

Content: This section outlines the BGP best path selection steps. It lists "Shortest AS-path" as a key step, followed by "Lowest origin code". The guide's command reference for best-path-selection as-path-ignore confirms that it causes the AS-path length step to be skipped, making the ORIGIN code the next major criterion.

2. Nokia 7750 SR and 7950 XRS Router Configuration Guide, Release 11.0.R1, Document Part Number: 3HE 08378 AAAC TQZZA 01.

Section: BGP > BGP Path Selection

Page: 218

Content: "The following is the BGP path selection process: ... 4. Select the path with the shortest AS-path. ... 5. Select the path with the lowest origin code (IGP < EGP < incomplete)." This document confirms the standard order of operations which is modified by the command in the question.