This read-only integer, part of the EZ2Boost router table, identifies the chassis slot associated with a discovered or configured external router being boosted; the source description is empty, so this reading is inferred from the object's name and its sibling objects such as ipEZ2BoostRouterBRAddress and ipEZ2BoostRouterType. An admin uses this slot number to physically locate which chassis slot corresponds to a given boosted-router table entry when doing hands-on troubleshooting. For example, an admin investigating why traffic through a particular boosted router entry stalled would use this slot value to find the correct physical card in the chassis.