This read-create object holds an alternate Bridge Priority value, the most significant 4 bits of a Bridge Identifier, used when this ISIS-SPB topology instance selects a shared tree root bridge under the given tie-break mask. An admin configures this to influence root-bridge election outcomes for specific ECT (Equal Cost Tree) algorithms in an SPBM network, separate from the bridge's normal STP priority. Setting a lower priority value here for one topology instance would make this bridge more likely to win root election for that specific ECT algorithm's shared tree.