BGP D-PATH and BGP best path selection

D-PATH is also considered for the BGP best path selection, as described in draft-ietf-bess-evpn-ipvpn-interworking.

As D-PATH is introduced in networks, not all the PEs may support D-PATH for BGP path selection. In order to guarantee compatibility in networks with PEs that do not support D-PATH the following command determines if the D-PATH should be considered for BGP best-path selection.

ex:/configure]
A:admin@PE-3# 
router “Base” bgp best-path-selection d-path-length-ignore <boolean> // default: false
service vprn <string> bgp best-path-selection d-path-length-ignore <boolean> // default: false
service vprn <string> d-path-length-ignore <boolean> // default: false

configure service system bgp evpn ip-prefix-routes d-path-length-ignore <boolean> // default: false

The following conditions apply to the d-path-length-ignore command usage:

• When d-path-length-ignore is configured at the base router level (or vprn>bgp level for PE-CE routes), BGP ignores the D-PATH domain segment length for best path selection purposes. This ignores d-path-length when comparing two VPN routes or two IFL routes within the same RD. These VPN or IFL routes are processed in main BGP instance.
• When d-path-length-ignore is configured at the VPRN router level, the VPRN RTM ignores the D-PATH domain segment length for best path selection purposes (for routes in VPRN).
• When d-path-length-ignore is configured at the service system bgp evpn ip-prefix-routes context, EVPN ignores the D-PATH length when iff-bgp-path-selection is enabled.
• When d-path-length-ignore is not configured, the D-PATH length is considered in the BGP best path selection process (at the BGP, the RTM, and IFF levels, respectively).