Which option forces traffic to take an explicit route across a backbone network?

IGP cost influences shortest-path selection among available routes but does not force traffic onto a specific explicit end-to-end path across the backbone.

The TE metric is a separate per-link metric configured specifically for MPLS Traffic Engineering path computation via CSPF; when a TE tunnel is established using an explicit path derived from TE metric values, traffic is forced to follow that specific route across the backbone regardless of IGP topology. This allows operators to direct traffic along predetermined paths for load balancing or policy enforcement independent of IGP cost.

TE affinity (link coloring or administrative groups) constrains path selection by including or excluding links from TE computations, but it does not force an explicit route by itself.

Running multiple IGPs provides routing domain separation but offers no mechanism to force traffic along a specific explicit path across a backbone network.