SR-TE Route Resolution to Color Only 'null' Routes (Color Mode = 01)

You can use colored SR-TE LSPs to simplify the mapping between MPLS services and the underlying transport based on SR-TE LSPs. In general, an operator assigns network layer reachability information (NLRI) color extended community to an MPLS service. When the next hop for such colored NRLI is being resolved on the ingress router, only SR-TE LSPs with a matching color value are taken into consideration as potential transport tunnels.

This feature further enhances the colored service mapping, by providing basic support for automatic fallback, when a colored path is not available. In addition to color, the BGP color extended community also carries color-only (CO) bits. The CO bits are used for encoding three different fallback next-hop resolution modes corresponding to the CO-bit value 00, 01, and 10.

This feature introduces fallback mode associated with CO-bits value 01, with the following resolution scheme:

• Resolve next hop through SR-TE LSPs with matching color, used for default route of the same address family as the next hop being resolved (that is, IPv4 or IPv6).
• Resolve next hop through SR-TE LSPs with matching color, used for default route of any address family (for example, IPv4 or IPv6).
• Resolve next hop through SR-TE LSPs with matching color and destination.
• Resolve through IGP path.