In one embodiment, a management device in a computer network determines when nodes of the computer network join any one of a plurality of field area routers (FARs), which requires a shared-media mesh security key for that joined FAR. The management device also maintains a database that indicates to which FAR each node in the computer network is currently joined, and to which FARs, if any, each node had previously joined, where the nodes are configured to maintain the mesh security key for one or more previously joined FARs in order to return to those previously joined FARs with the maintained mesh security key. Accordingly, in response to an updated mesh security key for a particular FAR of the plurality of FARs, the management node initiates distribution of the updated mesh security key to nodes having previously joined that particular FAR that are not currently joined to that particular FAR.