Explanation/Reference:
Explanation:
Given multiple possible routes to a particular destination, an L1 path is preferred over an L2 path. Within each level, a path that supports the optional metrics is preferred over a path that supports only the default metric. (Again, Cisco supports only the default metric, so the second order of preference is not relevant to Cisco routers.) Within each level of metric support, the path with the lowest metric is preferred. If multiple equal-cost, equal-level paths are found by the Decision process, they are all entered into the route table.
The Cisco IS-IS implementation usually performs equal-cost load balancing on up to six paths.
Reference: http://www.realccielab.org/operation-of-integrated-is-is.html