This is a colon-delimited list of the actual outbound interface indexes the circuit currently traverses at each node along its established path, in the format interface:interface:interface. An admin diagnosing intermittent packet loss on a circuit would decode cktPath to identify each hop's interface and then check per-interface error counters at those specific points rather than guessing. For example, a cktPath value like '4:12:7' tells the admin the circuit exits this node via interface 4, then interface 12 at the next node, then interface 7 at the node after that.