Jumbo is the three layer switch-box router based on Rivest and Fiduccia's greedy channel router. Jumbo uses three layers of wires to generate the solution with two choices: a. Two wiring layers for vertical routing and one for horizontal routingVHV b. Two wiring layers for horizontal routing and one for vertical routingHVH. The router scans first from left to right until no more split nets remain or reach the right hand side edge. If it hasn't reached the edge, then it scans in the opposite direction and stops at the column where it had stopped earlier where no more split nets had remained. Jumbo is capable of routing switchboxes and channels containing obstacles such as preexisting wiring by hand or by other routers. It jogs nets around multi-layer obstacles such as contacts, and routes over single-layer obstacles. If there are no obstacles, results for VHV channel routing are comparable to other good channel routers. Three layer HVH channel routing requires fewer tracks and even upto about half the number of tracks required by the two layer routing. Results from several benchmark examples are evaluated. Jumbo router found a 19 track VHV solution for Deutsch's difficult example. The computational complexity of the greedy algorithm is linearly proportional to the number of columns in a channel for the average case. Jumbo thus combines the effectiveness of traditional channel routers with the flexibility of net-at-a-time routers.